Method for purification of aromatic polyethers

ABSTRACT

Aromatic polyethers are prepared by displacement polymerization reaction in the presence of a water-immiscible solvent with boiling point at atmospheric pressure of greater than 110° C. and a density ratio to water of greater than 1.1:1 at 20-25° C. The polyethers are purified by processes comprising aqueous extraction, or filtration, or a combination thereof.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application is a continuation-in-part of copending U.S.application Ser. No. 09/634,161, filed Aug. 9, 2000, which claims thebenefit of U.S. Provisional Application No. 60/154,764, filed Sep. 20,1999, which applications are incorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002] The present invention relates to methods for purification ofaromatic polyethers, and more particularly to methods for purificationof aromatic polyetherimides.

[0003] Various types of aromatic polyethers, particularlypolyetherimides, polyethersulfones, polyetherketones, andpolyetheretherketones have become important as engineering resins byreason of their excellent properties. These polymers are typicallyprepared by the reaction of salts of dihydroxyaromatic compounds, suchas bisphenol A (BPA) disodium salt, with dinitroaromatic molecules ordihaloaromatic molecules. Examples of suitable dihaloaromatic moleculesinclude bis(4-fluorophenyl)sulfone, bis(4-chlorophenyl)sulfone, and theanalogous ketones and bisimides as illustrated by1,3-bis[N-(4-chlorophthalimido)]benzene.

[0004] According to U.S. Pat. No. 5,229,482, the preparation of aromaticpolyethers by displacement polymerization may be conducted in thepresence of a relatively non-polar solvent, using a phase transfercatalyst which is substantially stable under the temperature conditionsemployed. Suitable catalysts include ionic species such as guanidiniumsalts. Suitable solvents disclosed therein include o-dichlorobenzene,dichlorotoluene, 1,2,4-trichlorobenzene and diphenyl sulfone.

[0005] It is desirable to isolate aromatic polyether from a reactionmixture (or other type of mixture such as recovery from a mixed recyclestream solution) free from contaminating species that may affect thepolymer's final properties in typical applications. In a typical halidedisplacement polymerization process contaminating species often includealkali metal halide and other alkali metal salts, residual monomerspecies, and residual catalyst species. For maximum efficiency ofoperation it is desirable to recover any solvent employed and othervaluable compounds such as catalyst species, and to provide wastestreams which do not contaminate the environment. In particular it isoften desirable to recover alkali metal halide, especially sodiumchloride, for recycle to a brine plant for production of sodiumhydroxide and chlorine.

[0006] Many conventional techniques are used to purifypolymer-containing organic solutions. For instance, extraction withwater and settling by gravity in a mixer/settling tank have been usedfor removal of aqueous-soluble species. However, water extractionmethods will not work when the water phase emulsifies with or does notphase separate efficiently from the organic phase. The particular caseof polyethers in chlorinated aromatic hydrocarbon solvents oftenpresents special difficulties when mixing with water and separating bysettling. Depending upon such factors as polymer concentration andtemperature, the organic solution may be particularly viscous makingefficient washing with an aqueous phase difficult. Variations in eithertemperature of operation in the range of about 20-180° C. or in polymerconcentration may promote settling due to density differences, but thepresence of surface-active functional groups on the polymer may stillpromote emulsification, particularly the presence of ionic end-groupssuch as phenoxide and/or carboxylate left uncapped from thepolymerization process. Another constraint is that the time forseparation of the aqueous and organic phases must be fast, preferably onthe order of minutes, so that separation rates do not slow downproduction. A method is needed that minimizes emulsification and isrelatively fast for phase separation of the water and organic phases.

[0007] Dry filtration via filters or membranes has also been employedfor the removal of relatively large suspended solids frompolymer-containing organic solutions. The advantage is that no processwater is needed, but the disadvantage is that the filter type has to bechosen carefully to avoid a high pressure drop as the solids cakebuilds. Filtration is not feasible if the solid particles plug, blind,or go through the porous filter media. Easy back flushing of the filteris also required for fast turn-around and repeated use. Alkali metalhalides, such as sodium chloride, are typically insoluble in organicsolvents such as chlorinated aromatic hydrocarbons, but such halides maybe present as small suspended solid crystals that are difficult toremove by standard filtration methods. Furthermore, residual monomerspecies such as alkali metal salts of monomer or complexes of catalystand monomer may also be present which often cannot be efficientlyremoved by filtration alone.

[0008] Because of the unique separation problems involved, new methodsare needed for efficiently separating aromatic polyether products fromcontaminating species in chlorinated aromatic hydrocarbons. Methods arealso required for recycling the solvent and for recovering usefulcatalyst and alkali metal halide species from any final waste stream.

BRIEF SUMMARY OF THE INVENTION

[0009] After careful study the present inventors have discovered methodsfor purifying aromatic polyethers prepared in water-immiscible solventswith a density ratio to water of greater than about 1.1:1 at 20-25° C.These new methods also provide efficient recovery of solvent, alkalimetal halide, and valuable catalyst species.

[0010] In one of its aspects the present invention provides a method forpurifying a mixture comprising (i) an aromatic polyether reactionproduct made by a halide displacement polymerization process, (ii) acatalyst, (iii) an alkali metal halide, and (iv) a substantiallywater-immiscible organic solvent with boiling point at atmosphericpressure of greater than 110° C. and a density ratio to water of greaterthan 1.1:1 at 20-25° C., comprising the steps of:

[0011] (a) quenching the mixture with acid; and

[0012] (b) at least one step of contacting a polyether-containingorganic phase with water and separating a water-containing phase fromthe organic phase, which step comprises using at least one of aliquid/liquid centrifuge, a solid/liquid centrifuge, a counter-currentcontact apparatus, a liquid-liquid extractor, a liquid-liquid continuousextractor, an extraction column, a static mixer, a coalescer, ahomogenizer, or a mixing/settling vessel.

[0013] In another of its aspects the present invention provides a methodfor purifying a mixture comprising (i) an aromatic polyether reactionproduct made by a halide displacement polymerization process, (ii) acatalyst, (iii) an alkali metal halide, and (iv) a substantiallywater-immiscible organic solvent with boiling point at atmosphericpressure of greater than 110° C. and a density ratio to water of greaterthan 1.1:1 at 20-25° C., comprising the steps of:

[0014] (a) subjecting the mixture to at least one solid separation step;

[0015] (b) quenching the mixture with acid; and

[0016] (c) extracting the organic solution at least once with water.

[0017] In still another of its aspects the present invention provides amethod for purifying a mixture comprising (i) an aromatic polyetherreaction product made by a halide displacement polymerization process,(ii) a catalyst, (iii) an alkali metal halide, and (iv) a substantiallywater-immiscible organic solvent with boiling point at atmosphericpressure of greater than 110° C. and a density ratio to water of greaterthan 1.1:1 at 20-25° C., comprising: at least one solid separation step,and at least one ion exchange step.

[0018] In still another of its aspects the present invention provides amethod for purifying a mixture comprising (i) an aromatic polyetherreaction product made by a halide displacement polymerization process,(ii) a catalyst, (iii) an alkali metal halide, and (iv) a substantiallywater-immiscible organic solvent with boiling point at atmosphericpressure of greater than 110° C. and a density ratio to water of greaterthan 1.1:1 at 20-25° C., comprising the steps of:

[0019] (a) providing to the mixture an amount of water in a rangebetween about 0.005 wt. % and about 10 wt. % based on weight ofpolyether;

[0020] (b) mixing the phases, wherein a portion of alkali metal halideis in a form that can be separated by a solid separation step followingmixing; and

[0021] (c) subjecting the mixture to at least one solid separation step.

DETAILED DESCRIPTION OF THE INVENTION

[0022] The polyethers of the present invention are typically derivedfrom combining at least one dihydroxy-substituted aromatic hydrocarbonmoiety and at least one substituted aromatic compound of the formula(I):

Z(A¹—X¹)₂  (I)

[0023] wherein Z is an activating radical, A¹ is an aromatic radical andX¹ is fluoro, chloro, bromo, or nitro, in the presence of acatalytically active amount of a phase transfer catalyst. In onesuitable procedure at least one alkali metal salt of at least onedihydroxy-substituted aromatic hydrocarbon is combined with at least onesubstituted aromatic compound of generic formula (I). The alkali metalsalts of dihydroxy-substituted aromatic hydrocarbons which are employedare typically sodium or potassium salts. Sodium salts are frequentlyused for reason of their availability and relatively low cost. Said saltmay be employed in anhydrous form. However, in certain instances theemployment of a hydrate, such as the hexahydrate of the bisphenol Asodium salt, may be advantageous provided water of hydration is removedbefore the substituted aromatic compound is introduced.

[0024] Suitable dihydroxy-substituted aromatic hydrocarbons includethose having the formula (II):

HO—A²—OH  (II)

[0025] wherein A² is a divalent aromatic hydrocarbon radical. SuitableA² radicals include m-phenylene, p-phenylene, 4,4′-biphenylene,4,4′-bi(3,5-dimethyl)phenylene, 2,2-bis(4-phenylene)propane and similarradicals such as those which correspond to the dihydroxy-substitutedaromatic hydrocarbons disclosed by name or formula (generic or specific)in U.S. Pat. No. 4,217,438.

[0026] In various embodiments the A radical has the formula (III):

—A³—Y—A⁴—,  (III)

[0027] wherein each of A³ and A⁴ is a monocyclic divalent aromatichydrocarbon radical and Y is a bridging hydrocarbon radical in which oneor two atoms separate A³ from A⁴. The free valence bonds in formula(III) are usually in the meta or para positions of A³ and A⁴ in relationto Y. Compounds in which A² has formula (III) are bisphenols, and forthe sake of brevity the term “bisphenol” is sometimes used herein todesignate the dihydroxy-substituted aromatic hydrocarbons; it should beunderstood, however, that non-bisphenol compounds of this type may alsobe employed as appropriate.

[0028] In formula (III) the A³ and A⁴ values may be unsubstitutedphenylene, or halo or hydrocarbon-substituted derivatives thereof,illustrative substituents (one or more) being alkyl, alkenyl, bromo orchloro. Unsubstituted phenylene radicals are employed in certainembodiments. In some embodiments both A³ and A⁴ are p-phenylene,although both may be o- or m-phenylene or one o- or m-phenylene and theother p-phenylene.

[0029] The bridging radical, Y, is one in which one or two atomsseparate A³ from A⁴. Illustrative radicals of this type includegem-alkylene (alkylidene) radicals; methylene, cyclohexylmethylene,2-[2.2.1]-bicycloheptylmethylene, ethylene, isopropylidene,neopentylidene, cyclohexylidene, cyclopentadecylidene, cyclododecylideneand adamantylidene. Also included are unsaturated radicals.

[0030] Suitable dihydroxy-substituted aromatic hydrocarbons also includethose containing indane structural units such as represented by theformula (IV), which compound is3-(4-hydroxyphenyl)-1,1,3-trimethylindan-5-ol, and by the formula (V),which compound is 1-(4-hydroxyphenyl)-1,3,3-trimethylindan-5-ol:

[0031] Also included among suitable dihydroxy-substituted aromatichydrocarbons are the 2,2,2′,2′-tetrahydro-1,1′-spirobi[1H-indene]diolshaving formula (VI):

[0032] wherein each R¹ is independently selected from monovalenthydrocarbon radicals and halogen radicals; each R², R³, R⁴, and R⁵ isindependently C₁₋₆ alkyl; each R⁶ and R⁷ is independently H or C₁₋₆alkyl; and each n is independently selected from positive integershaving a value of from 0 to 3 inclusive. A particular2,2,2′,2′-tetrahydro-1,1′-spirobi[1H-indene]-diol is2,2,2′,2′-tetrahydro-3,3,3′,3′-tetramethyl-1,1′-spirobi[1H-indene]-6,6′-diol.

[0033] Some illustrative examples of dihydric phenols of formula (II)include 6-hydroxy-1-(4′-hydroxyphenyl)-1,3,3-trimethylindane,4,4′-(3,3,5-trimethylcyclohexylidene)diphenol;1,1-bis(4-hydroxy-3-methylphenyl)cyclohexane;2,2-bis(4-hydroxyphenyl)propane (commonly known as bisphenol-A);2,2-bis(4-hydroxy-3,5-dimethylphenyl)propane;4,4-bis(4-hydroxyphenyl)heptane;2,2-bis(4-hydroxy-3-methylphenyl)propane;2,2-bis(4-hydroxy-3-ethylphenyl)propane;2,2-bis(4-hydroxy-3-isopropylphenyl)propane;3,5,3′,5′-tetrachloro-4,4′-dihydroxyphenyl)propane; 2,4′-dihydroxyphenylsulfone; 2,4′-dihyroxydiphenylmethane; bis(2-hydroxyphenyl)methane;bis(4-hydroxyphenyl)methane; bis(4-hydroxy-5-nitrophenyl)methane;bis(4-hydroxy-2,6-dimethyl-3-methoxyphenyl)methane;1,1-bis(4-hydroxyphenyl)ethane; 1,1-bis(4-hydroxy-2-chlorophenyl)ethane;2,2-bis(3-phenyl-4-hydroxyphenyl)propane;bis(4-hydroxyphenyl)cyclohexylmethane;2,2-bis(4-hydroxyphenyl)-1-phenylpropane; 2,6-dihydroxynaphthalene;hydroquinone; resorcinol; C₁₋₃ alkyl-substituted resorcinols. Forreasons of availability and particular suitability the preferreddihydric phenol is in some embodiments bisphenol A in which the radicalof formula (III) is the 2,2-bis(4-phenylene)propane radical and in whichY is isopropylidene and A³ and A⁴ are each p-phenylene.

[0034] The substituted aromatic compounds of formula (I) which areemployed in the present invention contain an aromatic radical A¹ and anactivating radical Z. The A¹ radical is normally a di- or polyvalentC₆₋₁₀ radical, which in various embodiments may be monocyclic and freefrom electron-withdrawing substituents other than Z. Unsubstituted C₆aromatic radicals may be employed for the A¹ radical.

[0035] The radical Z is one which activates a leaving group X on anaromatic radical for displacement by alkali metal salts ofdihydroxy-substituted aromatic hydrocarbons. The Z radical is usually anelectron-withdrawing group, which may be di- or polyvalent to correspondwith the valence of A¹. Illustrative examples of divalent radicalsinclude carbonyl, carbonylbis(arylene), sulfone, bis(arylene)sulfone,benzo-1,2-diazine and azoxy. Illustrative examples of the moiety—A¹—Z—A¹— include bis(arylene)sulfone, bis(arylene)ketone,tris(arylene)bis(sulfone), tris(arylene)bis(ketone),bis(arylene)benzo-1,2-diazine or bis(arylene)azoxy radical andespecially those in which A¹ is p-phenylene.

[0036] Also included are compounds in which —A¹—Z—A¹— is a bisimideradical, illustrated by those of the formula (VII):

[0037] wherein R⁸ is a substituted or unsubstituted C₆₋₂₀ divalentaromatic hydrocarbon radical, a C₂₋₂₂ alkylene or cycloalkylene radical,or a C₂₋₈ bis(alkylene-terminated)polydiorganosiloxane radical.

[0038] In one embodiment of the invention R⁸ is derived from a diamineselected from the group consisting of aliphatic, aromatic, andheterocyclic diamines. Exemplary aliphatic moieties include, but are notlimited to, straight-chain-, branched-, and cycloalkyl radicals, andtheir substituted derivatives. Straight-chain and branched alkylradicals are typically those containing from 2 to 22 carbon atoms, andinclude as illustrative non-limiting examples ethyl, propyl, butyl,neopentyl, hexyl, dodecyl. Cycloalkyl radicals are typically thosecontaining from 3 to 12 ring carbon atoms. Some illustrativenon-limiting examples of cycloalkyl radicals include cyclobutyl,cyclopentyl, cyclohexyl, methylcyclohexyl, and cycloheptyl.

[0039] In various embodiments the two amino groups in diamine-derivedaliphatic moieties are separated from each other by at least two andsometimes by at least three carbon atoms. In particular embodiments fordiamines, the two amino groups are in the alpha, omega positions of astraight-chain or branched alkyl radical, or their substitutedderivatives; or in the 1,4-positions of a cycloalkyl radical or itssubstituted derivatives. In various embodiments substituents for saidaliphatic moieties include one or more halogen groups, such as fluoro,chloro, or bromo, or mixtures thereof; or one or more aryl groups, suchas phenyl groups, alkyl- or halogen-substituted phenyl groups, ormixtures thereof. In some embodiments substituents for aliphaticmoieties, when present, are chloro or unsubstituted phenyl.

[0040] Aromatic moieties suitable for R⁸ in formula (VII) include, butare not limited to, monocyclic, polycyclic and fused aromatic compoundshaving in some embodiments from 6 to 20, and in other embodiments from 6to 18 ring carbon atoms, and their substituted derivatives. Polycyclicaromatic moieties may be directly linked by a covalent bond (such as,for example, biphenyl) or may be separated by 1 or 2 atoms comprisinglinking moieties as in formula (VIII):

[0041] or a covalent bond. Representative linking moieties may alsoinclude phosphoryl, S, and C₁₋₆ aliphatic, such as isopropylidene andmethylene. Illustrative non-limiting examples of aromatic moietiesinclude phenyl, biphenyl, naphthyl, bis(phenyl)methane,bis(phenyl)-2,2-propane, and their substituted derivatives. Inparticular embodiments substituents include one or more halogen groups,such as fluoro, chloro, or bromo, or mixtures thereof; or one or morestraight-chain-, branched-, or cycloalkyl groups having from 1 to 22carbon atoms, such as methyl, ethyl, propyl, isopropyl, tert-butyl, ormixtures thereof. In particular embodiments substituents for aromaticmoieties, when present, are at least one of chloro, methyl, ethyl ormixtures thereof.

[0042] In various embodiments the two amino groups in diamine-derivedaromatic moieties are separated by at least two and sometimes by atleast three ring carbon atoms. When the amino group or groups arelocated in different aromatic rings of a polycyclic aromatic moiety,they are often separated from the direct linkage or from the linkingmoiety between any two aromatic rings by at least two and sometimes byat least three ring carbon atoms. In some embodiments diamines for thepresent invention include meta-phenylenediamine; para-phenylenediamine;mixtures of meta- and para-phenylenediamine; isomeric 2-methyl- and5-methyl-4,6-diethyl-1,3-phenylenediamines or their mixtures;bis(4-diaminophenyl)-2,2-propane; andbis(2-chloro-4-amino-3,5-diethylphenyl)methane.

[0043] Heterocyclic moieties suitable for R⁸ in formula (VII) include,but are not limited to, monocyclic, polycyclic and fused heterocycliccompounds having in some embodiments from 3 to 30, in other embodimentsfrom 5 to 13 ring carbon atoms, and 1 to 4 ring heteroatoms. The ringheteroatoms include, but are not limited to, oxygen, nitrogen, sulfur,or combinations thereof. In some embodiments ring heteroatoms arenitrogen. Polycyclic heterocyclic moieties may be directly linked by acovalent bond (such as, for example, bipyridyl) or may be separated by 1or 2 atoms comprising linking moieties. Representative linking moietiesinclude, but are not limited to, carbonyl, phosphoryl, O, S, SO₂, C₁₋₆aliphatic, such as isopropylidene and methylene.

[0044] In various embodiments the two amino groups in diamine-derivedheterocyclic moieties are separated by at least two and sometimes by atleast three ring atoms. When the amino group or groups are located indifferent heterocyclic rings of a polycyclic heterocyclic moiety, theyare separated from the direct linkage or from the linking moiety betweenany two heterocyclic rings by at least two and sometimes by at leastthree ring atoms. Exemplary heterocyclic moieties include, but are notlimited to, furyl, pyridyl, bipyridyl, pyrryl, pyrazinyl, pyrimidyl,pyrazolyl, thiazyl, thienyl, bithienyl, and quinolyl.

[0045] Most often, R⁸ is at least one of m-phenylene, p-phenylene,4,4′-oxybis(phenylene) or

[0046] Polyvalent Z radicals include those in which Z together with A¹form part of a fused ring system such as benzimidazole, benzoxazole,quinoxaline or benzofuran.

[0047] Also present in the substituted aromatic compound of formula (I)are two displaceable X¹ radicals which may be fluoro, chloro, bromo, ornitro. In most instances, fluoro and especially chloro atoms areemployed by reason of the relative availability and effectiveness of thecompounds containing them. The relative positions of the two X¹ radicalson two aromatic rings are such that they are activated for displacementby alkali metal salts of dihydroxy-substituted aromatic hydrocarbons.The two X¹ radicals are often each in the para position or each in themeta position or one substituent is in the para position and one in themeta position relative to the an activating group Z on an aromatic ring(or relative to a second aromatic group attached to an activating groupZ on an aromatic ring).

[0048] In various embodiments substituted aromatic compounds of formula(I) include but are not limited to bis(4-fluorophenyl)sulfone and thecorresponding chloro compound; bis(4-fluorophenyl)ketone and thecorresponding chloro compound; and 1,3- and1,4-bis[N-(4-fluorophthalimido)]benzene, and 1,3- and1,4-bis[N-(3-fluorophthalimido)]benzene; and4,4′-bis[N-(4-fluorophthalimido)]phenyl ether, and4,4′-bis[N-(3-fluorophthalimido)]phenyl ether; and the correspondingchloro and bromo compounds, especially at least one of1,3-bis[N-(4-chlorophthalimido)]benzene,1,4-bis[N-(4-chlorophthalimido)]benzene,1,3-bis[N-(3-chlorophthalimido)]benzene,1,4-bis[N-(3-chlorophthalimido)]benzene,1-[N-(4-chlorophthalimido)]-3-[N-(3-chlorophthalimido)benzene, or1-[N-(4-chlorophthalimido)]-4- [N-(3-chlorophthalimido)benzene.

[0049] Also present in the polymer-containing mixture is at least onephase transfer catalyst, which in various embodiments is substantiallystable at the temperatures employed; i.e., in the range of about125-250° C. Various types of phase transfer catalysts may be employedfor this purpose. They include quaternary phosphonium salts of the typedisclosed in U.S. Pat. No. 4,273,712, N-alkyl-4-dialkylaminopyridiniumsalts of the type disclosed in U.S. Pat. Nos. 4,460,778 and 4,595,760,and guanidinium salts of the type disclosed in the aforementioned U.S.Pat. No. 5,229,482. In some embodiments the phase transfer catalysts, byreason of their exceptional stability at high temperatures and theireffectiveness to produce high molecular weight aromatic polyetherpolymers in high yield, comprise the hexaalkylguanidinium andalpha,omega-bis(pentaalkylguanidinium)alkane salts, particularly thechloride salts. In a particular embodiment the catalyst is1,6-bis(penta-n-butylguanidinium)hexane dibromide. In another particularembodiment the catalyst is hexaethylguanidinium chloride.

[0050] At least one substantially water-immiscible organic solvent mayalso be present in the polymer-containing mixture. Said at least onesolvent may completely or at least partially dissolve reactioningredients. Within the context of the present invention suitablesolvents are those which have a boiling point at atmospheric pressure ofin one embodiment greater than 110° C. (and in another embodimentgreater than about 125° C.) and a density which is in one embodiment ina ratio of greater than 1.1:1, in another embodiment greater than1.15:1, and in still another embodiment greater than 1.2:1 compared tothe density of water at 20-25° C. (which is 0.997 grams per cubiccentimeter). Substantially water-immiscible means that the organicsolvent dissolves to the extent of in one embodiment less than about 10wt. % and in another embodiment less than about 5 wt. % in water, orthat water dissolves to the extent of in one embodiment less than about10 wt. % and in another embodiment less than about 5 wt. % in theorganic solvent. In some embodiments solvents are aromatic hydrocarbons,and particularly halogenated aromatic hydrocarbons. In particularembodiments solvents include diphenylsulfone, chlorinated benzenes, suchas chlorobenzene, dichlorotoluene, 1,2,4-trichlorobenzene, andespecially o-dichlorobenzene (hereinafter often referred to as ODCB).Mixtures of such solvents may also be employed.

[0051] In one embodiment the method of the present invention comprisescontacting a polyether-containing organic phase with water andseparating a water-containing phase from the organic phase. In someembodiments contacting with and separating a water-containing phase fromthe organic phase is essentially a liquid/liquid process which includesthe process of extraction of liquid organic phase with water. In otherembodiments contacting with and separating a water-containing phase fromthe organic phase is a solid/liquid process wherein the water-containingphase comprises a solid phase that can be separated by a solidseparation method as described hereinbelow. Such methods may beperformed in a batch, semi-continuous, or continuous mode.

[0052] In various embodiments contaminating species may be transferredfrom the organic to the aqueous phase during contact with water. Contactwith and separation from water typically comprises at least threesecondary processes: creation of sufficient surface area between waterand organic phases for optimum contact while minimizing emulsionformation; transfer of water-soluble species from organic to waterphases; and separation of water and organic phases. Typicalwater-soluble species which may be transferred include alkali metalhalide and other alkali metal salts, ionic catalyst species and catalystdecomposition products, and residual monomer species. Contact with andseparation from water may be performed using known methods andapparatus, including known methods for liquid-liquid contacting. In someembodiments contact with water is performed using a counter-currentcontact method with fresh water first contacting organic phasecontaining the lowest concentrations of water-soluble species (such assodium chloride and ionic catalyst species). Any known method forperforming counter-current extraction of a heavier-than-water organicphase with water may be used. Contact with and separation from watermethods also include those which employ, either separately or in series,one or more of mixer/settling vessels such as mixing/settling tanks,in-pipe static mixers, liquid droplet coalescers, extraction columns,liquid-liquid extractors, counter-current contact apparatus,homogenizers, and liquid-liquid centrifuges, or combinations thereof.Temperatures at which such processes may be performed refer to theentire process and particularly to the secondary process of separation.

[0053] In some embodiments prior to any purification step which involvescontact with and separation from water, a polyether-containing reactionmixture is quenched with acid. Quenching with acid may be performedeither before or after any solid separation step, such as filtration,that may be employed. The acid can be in solid, liquid, gaseous, orsolution form. Suitable acids include organic acids such as acetic acid,and inorganic acids such as phosphorous acid, phosphoric acid, oranhydrous hydrochloric acid. A gaseous acid, such as anhydroushydrochloric acid, can be bubbled into the reaction mixture through asparger or delivered as a solution in a convenient solvent such in thesame organic solvent as used in the reaction mixture. The quantity ofacid added is in various embodiments at least sufficient to react withthe calculated amount of phenoxide end-groups that will be present for agiven molecular weight of polyether product. In other embodiments thequantity of acid added is greater than the calculated amount and instill other embodiments about twice the calculated amount of phenoxideend-groups that will be present for a given molecular weight ofpolyether product.

[0054] The acid may be added using any convenient protocol. Typically, agaseous acid is added over time, said time being dependent upon factorsknown to those skilled in the art, including the volume of the reactionmixture and the concentration of polyether product among other factors.The time of addition is typically less than about 60 minutes, moretypically less than about 20 minutes, and still more typically less thanabout 10 minutes. The temperature of the reaction mixture during acidaddition may vary from about room temperature to a temperature above theboiling point of the organic solvent (in which latter case the mixtureis under pressure), and more typically from about room temperature toabout the boiling point of the organic solvent, in some embodiments fromabout 50° C. to about 210° C., in other embodiments from about 60° C. toabout 180° C. and in still other embodiments from about 90° C. to about140° C. Following acid quenching, the polymer-containing mixture may betaken directly to any subsequent steps or may be stirred for aconvenient period, which in some embodiments may be about 30-60 minutes.

[0055] The quenching step typically converts surface-active species, forexample phenoxide salts of alkali metal and/or catalyst cationicspecies, to non-surface-active phenolic groups. This quenching step alsopermits more efficient recovery of any polymer-bound catalyst cationicspecies by converting them to salts which are more easily recovered fromthe polymer-containing mixture, such as chloride salts. In the case ofpolyetherimide-containing reaction mixtures quenching is also importantin converting any residual carboxylate salts to carboxylic acids whichcan ring-close to imide during subsequent processing steps resulting inhigher polymer stability. The quenching step also helps deter emulsionformation during subsequent water extraction through removal of surfaceactive species.

[0056] In one embodiment the method of the present invention comprisessubjecting the polyether-containing mixture to at least one extractionwith water following acid quenching. Water extraction may be performedusing a mixer and settling tank combination. An advantage of thiscombination is that the required equipment is simple, requiring animpeller or other dynamic mixing device, and a tank of proper geometry.

[0057] In a particular embodiment a mixer/settling tank is filled with apolyetherimide/o-dichlorobenzene solution comprising sodium chloride andat least one catalyst, such as a hexaalkylguanidinium chloride. Thepolymer-containing mixture is brought to a temperature in one embodimentin the range of about 25-205° C., in another embodiment in the range ofabout 60-180° C., in another embodiment in the range of about 70-120°C., and in still another embodiment in the range of about 85-105° C.Water is added to the tank and stirring is applied. The temperature ismaintained in the ranges mentioned above. If desired, water may bepreheated before addition to the organic phase, or a water-organicmixture may be reheated to a desired temperature range. Whentemperatures above the effective boiling point (at atmospheric pressure)of the mixture are employed, then the tank is typically enclosed underpressure during any water addition and extraction step. In these casestypical pressures are about 1 to about 280 psi.

[0058] Brine formation is desirably achieved under conditions whichminimize the amount of water used and which favor rapid phase separationof aqueous and organic phases. Typical phase ratios are in someembodiments about 0.5-6 parts of organic phase to one part water byweight. In a particular embodiment the phase ratio is about 5 parts oforganic phase to one part water by weight. The desired stirring rate isbelow the rate at which emulsification of the mixture occurs. Moreparticularly, the stirring rate must provide sufficient contact betweenthe phases so that adequate mass transfer occurs without too large aninterfacial area being generated. Typical stirring rates are such as toprovide Reynolds numbers of in some embodiments about 25-500 and inother embodiments about 50-100.

[0059] In one embodiment the stirrer is stopped after a few minutes ofstirring and the ODCB/water mixture is allowed to settle. The ODCB layeris typically the bottom layer. Some of the sodium chloride dissolves inthe water and some remains in the ODCB phase, typically as crystals.This first extraction typically achieves up to about 70-99.9% sodiumchloride removal from an ODCB phase, and more typically about 90-99.9%.The first extraction also typically removes about 50-99.9% of any ioniccatalyst present. In particular embodiments the first extractionachieves greater than 99.9% removal of sodium chloride and of ioniccatalyst.

[0060] In some embodiments the aqueous phase is separated withoutincluding any emulsified material or emulsified layer (hereinaftersometimes referred to as “rag layer”) that may be present, and saved forcatalyst, monomer species, and sodium chloride recovery by conventionalmeans (for instance, using a coalescer). The formation of rag layer maybe affected by such variables as the ratio of aqueous phase to organicphase, the time and intensity of stirring, the concentration of alkalimetal halide, the concentration of polymer, the concentration ofunquenched polymer end-groups, and the temperature among other factors.Any rag layer, if present, may be separated and transferred to aseparate vessel for later addition to the next batch of polymer mixturefor purification, or left together with the organic phase for a secondextraction. The organic phase remaining may be subjected to a secondextraction or other purification step, if further purification isdesired, or sent to a polymer isolation step where the solvent iscompletely removed from the solution.

[0061] In another embodiment the organic phase after any extraction withwater is heated before any subsequent contact with and separation fromwater. The temperature to which the organic phase is heated is in someembodiments higher than that temperature of the organic phase at which aprevious extraction was performed. The temperature to which the organicphase is heated is in other embodiments higher than that temperature atwhich any subsequent extraction is performed. The temperature to whichand time for which the organic phase is heated is in still otherembodiments a temperature and time sufficient to render the organicphase substantially transparent and in still other embodiments atemperature and time sufficient to substantially break any emulsion thatmay be present such that either the organic phase becomes substantiallyhomogeneous or any residual water separates from the organic phase, orboth. The temperature is in one embodiment in a range between about 60°C. and the boiling point of the organic phase under the prevailingconditions, in another embodiment in a range between about 90° C. andabout 180° C., in still another embodiment in a range between about 100°C. and about 160° C., in still another embodiment in a range betweenabout 110° C. and about 150° C., and in still another embodiment in arange between about 120° C. and about 150° C. Following heating of theorganic phase to a temperature in the desired range, the temperature istypically lowered to a temperature in a range for a subsequentextraction with water.

[0062] If higher levels of purification are desired, one or moreadditional water contact and separation steps may be performed, forexample in one embodiment using mixing/settling, for example in the samevessel. A ratio of in one embodiment about 0.5-6:1 (weight/weight)organic phase to water and in another embodiment about 5:1(weight/weight) organic phase to water is used. Mixing includesstirring. The desired stirring rate is below the rate at whichemulsification of the polymer-containing mixture occurs. Moreparticularly, the stirring rate must provide sufficient contact betweenthe phases so that adequate mass transfer occurs without too large aninterfacial area being generated. Typical stirring rates are such as toprovide Reynolds numbers of in some embodiments about 25-500 and inother embodiments about 50-100.

[0063] In addition, any extraction after a first extraction is performedin some embodiments in the temperature range of about 25-205° C., inother embodiments in the range of about 60-180° C., and in still otherembodiments in the range of about 80-100° C. A second water extractionprocess typically achieves in some embodiments up to about 90-99.9% andin other embodiments greater than about 99.9% residual sodium chlorideand ionic catalyst removal from an organic phase (based on the weightsodium chloride and catalyst remaining after a first extraction).

[0064] In another embodiment a second (or subsequent) water extractionstep can be carried out by a process which comprises sparging steamthrough the organic phase under pressure. The steam temperature has avalue of less than the boiling point of organic phase under the processconditions, and in some embodiments is a temperature of about 110-175°C., and in other embodiments a temperature of about 140° C. The organicmixture has in some embodiments a temperature of about 25-175° C., andin other embodiments a temperature of about 110° C. The amount of steamsparged per minute is typically such as to provide a volume/volume ratioof organic phase to steam in some embodiments in a range of betweenabout 0.5:1 and about 10:1; in other embodiments in a range of betweenabout 1:1 and about 7:1 and in other embodiments in a range of betweenabout 2:1 and about 5:1. In a typical process steam is sparged in someembodiments for about 1-60 minutes; in other embodiments for about 10-60minutes and in other embodiments for about 30 minutes. Steam may bevented from the container through a pressure relief valve. Any organicphase that happens to be removed along with the escaping steam may berecovered using standard methods.

[0065] As the steam rises, it will typically carry upwards any residualentrained water droplets remaining from a first (or subsequent)extraction, thus further increasing the sodium recovery efficiency. Asdescribed above, the aqueous phase may typically collect at the top ofthe organic phase. The organic phase may then be removed from the bottomof the vessel leaving the aqueous phase behind after which said aqueousphase may be treated in a manner as described hereinafter. More than onestep comprising steam sparging of an organic phase may be employed.

[0066] In another embodiment a static mixer can be used in conjunctionwith or as an alternate approach to a dynamic mixer/settling tank in apurification process comprising water extraction. The advantages ofstatic mixers are that a milder degree of mixing is often possible byminimizing shear forces and avoiding smaller droplet formation andpossible emulsification. Various process configurations can be employedwhen at least one step in the process uses a static mixer. For example,a static mixer can be used for a first extraction with water, or for allextractions with water, or for one or more subsequent extractions withwater following a first extraction that employs a dynamic mixer/settlingtank combination.

[0067] The usefulness of a static mixer may be greater for performing asecond or subsequent extraction following a first water extraction,since often with second and/or subsequent extractions the emulsificationtendencies may be greater. Employing a static mixer for at least oneextraction step may be particularly useful when a polymer mixtureproduces a larger than usual rag layer or emulsifies abnormally, or whenthe purification process comprises adding rag layer either to asubsequent extraction after a first extraction or to a next polymermixture, and the volume of rag layer continues to increase as the numberof batches increases. Since in many embodiments rag layers representabout 10% (by volume) or less of any aqueous phase volume (or less thanabout 2% (by volume) of the organic phase), the use of additional waterinjected into any rag layer as it is removed from a holding tank, forexample, for pumping through a static mixer is not a serious penalty tothe process operation. The two phases can then be separated andrecovered by such means as in a coalescer filter medium. A staticmixer/coalescer combination can also be used in parallel to thehereinabove described processes of one or more water extraction steps(including the steam sparging option), optionally with a subsequentfiltration step. In one embodiment a dynamic mixer/settling tankcombination may separate the bulk of the two phases while a staticmixer/coalescer reclaim the polymer solution from any rag layer formed.In another embodiment a dynamic mixer/settling tank combination mayseparate the bulk of the two phases and the organic phase (optionallywith rag layer) may then be passed at least once through a recycle loopcomprising a static mixer with water injection at a level of about0.5-7:1 organic:water (weight/weight). The treated polymer-containingmixture may then return to a tank for settling or other treatment asdescribed hereinabove. An advantage of such processes is that a staticmixer can be used to perform the mixing in a transfer pipe in a matterof seconds, rather than minutes as in a mixer tank, and a liquid-liquidcoalescer filter can be used in parallel with or instead of a settlingtank to perform the separation of organic from water.

[0068] In a particular embodiment a polyetherimide-containing ODCBsolution may be pumped out of a holding tank to a static mixer, where itmay be combined with a stream of water in a predetermined ratio and putthrough a static mixer. The amount of water added may be in oneembodiment about 0.5-7:1 and in another embodiment about 5:1 ODCB:water(weight/weight ratio). The speed of pumping is determined by the desiredReynolds number in the static mixer. Reynolds numbers less than 500 willtypically result in mild interphase contact approaching laminar flow asthe Reynolds number goes to zero. More vigorous contacting will beobtained in turbulent flow above 2000 Reynolds Number. By adjusting thelength of the static mixer the contact time between the two phases canbe controlled. The contact time is typically on the order of seconds.Because of the action of the static mixer resembles end-over-end orside-by-side motion rather than a shearing motion as in a stirrer,emulsification is inhibited.

[0069] In a particular embodiment contact between ODCB phase and waterphase in a static mixer is performed at temperatures of about 25-175°.Typical pressures are about 1-280 psi. The mixed system may then be sentdirectly to a coalescer, particularly if the time for phase separationin a settling tank is longer than desired. The coalescer may be operatedat a temperature similar to or different from that of thepolymer-containing mixture to be separated. The use of a coalescer mayrequire a temperature as high as possible (for example, as high as about90° C.) to reduce viscosity, and an ODCB-to-water ratio of less than1:1, for instance, since coalescers are typically only effective foroil-in-water emulsions. A prefilter may be required to remove solidparticles, for example of residual monomer, prior to using a coalescer.Alternatively, a settling tank can be used instead of a coalescer. Inthe settling tank, the aqueous phase is continuously decanted at thetop, the organic phase is continuously sent to polymer isolation wherethe ODCB may be evaporated from the polymer.

[0070] In still another embodiment contact of polyether-containingorganic phase with water may be performed in a liquid-liquid extractioncolumn, whereby sodium chloride and other water soluble species areextracted into the water phase from the organic phase. Typicallyoperation of such a column comprises contact between two immiscibleliquids in counter-current manner, for example, with the less densephase moving upward and the more dense phase moving downward. The columnis typically filled with a packing to increase surface area, such asballs, rings, saddles, or other material known in the art. Other methodsfor improving column efficiency comprise inclusion in the column ofperforated plates attached to a central rod which may be oscillated, orinclusion in the column of alternating sections of mixing zones anddecanting zones. Operation of a liquid-liquid extraction column in thepresent context is at a temperature in a range in one embodiment betweenabout 60° C. and about 150° C., in another embodiment between about 70°C. and about 120° C., and in still another embodiment between about 80°C. and about 100° C. Optionally the extraction column may be operatedunder pressure. Feed ratios are in some embodiments in a range of about5:1 (wt./wt.) to 1:5 (wt./wt.) organic phase to aqueous phase, and inother embodiments in a range of about 3:1 (wt./wt.) to 1:3 (wt./wt.)organic phase to aqueous phase.

[0071] The aqueous phase from any extraction step by any method may beremoved and sent for recycling, waste water treatment, and/or to atleast one recovery step (for example, processing in a coalescer) forrecovery of such species as catalyst and traces of organic solvent. Inone embodiment two or more aqueous fractions from different extractionsare combined for recovery of such species as catalyst, monomer, and anytraces of organic solvent. Any small, water-insoluble particles that mayremain in the organic phase after separation from a water phase may beremoved by a solid separation step as described hereinafter.

[0072] In a particular embodiment hexaalkylguanidinium chloride catalystfrom a polyetherimide preparation may be recovered for reuse from one ormore aqueous fractions by mixing with ODCB and removing water bydistillation until substantially all the water is removed. Thedistillation may be further continued until a desired concentration ofcatalyst in ODCB and a desired residual water level are obtained. Ifnecessary, additional ODCB may be added to the distillation residue asrequired. The amount of recovered catalyst in ODCB is typically anamount in a range of between about 5% and about 99%, more typically in arange of between about 40% and about 98%, and still more typically in arange of between about 50% and about 90% of the original amount ofcatalyst added to a reaction mixture. Concentrations of residual waterare in some embodiments less than 100 ppm, and in other embodiments lessthan 50 ppm. If there are any water-insoluble particles in thecatalyst-containing ODCB phase after distillation, they may be removedby filtration as described hereinafter.

[0073] The purification methods of the present invention may compriseone or more solid separation steps, such as, but not limited to,filtration, sedimentation and decantation, or solid/liquidcentrifugation. Such a process may be performed in a batch,semi-continuous, or continuous mode. Any known filtration method may beused. For example, filtration may be performed using at least one of adead-end filter, cross-flow filter, liquid-solid cyclone separator,vacuum drum filter, centrifuge, or vacuum conveyor belt separator. Inparticular, suitable filtration methods include those described in“Chemical Engineer's Handbook”, (Robert H. Perry and Cecil H. Chilton,editors; McGraw Hill, publishers). In one embodiment a purificationprocess may comprise at least one dry filtration step (that is, afiltration of a polyether-containing organic phase substantially free ofwater) as described hereinafter. Any solid separation step may beperformed at a temperature in one embodiment in a range of between aboutroom temperature and about the boiling point of the organic phase underthe prevailing conditions, in other embodiments in a range of betweenabout 25° C. and about 220° C., in other embodiments in a range ofbetween about 25° C. and about 180° C., in other embodiments in a rangeof between about 60° C. and about 180° C., in other embodiments in arange of between about 80° C. and about 160° C., in other embodiments ina range of between about 80° C. and about 140° C., in other embodimentsin a range of between about 85° C. and about 120° C., in otherembodiments in a range of between about 85° C. and about 110° C., and inother embodiments in a range of between about 90° C. and about 105° C.One effect of using elevated temperature is to decrease the mixtureviscosity to facilitate processes such as filtration.

[0074] In another embodiment a purification process may comprise atleast one solid separation step, such as filtration, which comprisesproviding a small amount of water to a polyether-containing organicphase and mixing the phases before solid separation. In one embodimentthe polymer-containing solution is quenched with acid before addition ofwater. Typically water is provided at a temperature in some embodimentsin the range of about 25-110° C., in other embodiments in the range ofabout 60-105° C., and in still other embodiments in the range of about80-100° C. In one embodiment water may be supplied as steam. Water isadded to the vessel holding polymer solution and mixing (such asstirring) is applied. If desired, water may be preheated before additionto the organic phase, or a water-organic mixture may be reheated to adesired temperature range. The amount of water added is in someembodiments in a range between about 0.005 wt. % and about 10 wt. %, inother embodiments in a range between about 0.01 wt. % and about 10 wt.%, in other embodiments in a range between about 0.05 wt. % and about 10wt. %, in other embodiments in a range between about 0.05 wt. % andabout 8 wt. %, in other embodiments in a range between about 0.1 wt. %and about 5 wt. %, in other embodiments in a range between about 0.3 wt.% and about 5 wt. %, in still other embodiments in a range between about0.5 wt. % and about 5 wt. %, and in still other embodiments in a rangebetween about 0.5 wt. % and about 1 wt % based on weight of polyether inthe organic solution. In certain other embodiments of the invention theamount of water added is in a range between about 0.3 wt. % and about 3wt. % based on weight of polyether in the organic solution. Although theinvention is not limited by any theory of operation, it is believed thatthe added water interacts upon contact with the hydrophilic alkali metalhalide crystals (such as sodium chloride crystals) and forms liquidbridges that promote further agglomeration. The agglomerated crystalscontaining the water phase can then be separated using any known solidseparation method, in some embodiments by solid/liquid centrifugation orfiltration or decantation. In a particular embodiment apolyetherimide-containing ODCB reaction mixture is treated with water,mixed, optionally allowed to settle, and filtered (or decanted) asdescribed, and the permeate from said filtration can then be subjectedto further purification steps, if so desired, including, for example,extraction one or more times with water as described above. In someembodiments substantially all or at least a portion of alkali metalhalide may be removed before any extraction of the polyether-containingorganic solution with water.

[0075] In another embodiment a purification process may comprise atleast one solid separation step which comprises providing a small amountof water to a polyether-containing organic phase and then heating themixture to a temperature of at least the boiling point of water underthe process conditions and subsequently separating solid such as byfiltering. In various embodiments water may be supplied as liquid,optionally preheated, or as steam. Water may also be provided asresidual water remaining with organic phase after at least one waterextraction of the organic phase. Water may also be provided in quenchingthe reaction mixture with acid. The amount of water added is in someembodiments in a range between about 0.005 wt. % and about 10 wt. %, inother embodiments in a range between about 0.01 wt. % and about 10 wt.%, in other embodiments in a range between about 0.05 wt. % and about 10wt. %, in other embodiments in a range between about 0.05 wt. % andabout 8 wt. %, in other embodiments in a range between about 0.1 wt. %and about 5 wt. %, in other embodiments in a range between about 0.3 wt.% and about 5 wt. %, in still other embodiments in a range between about0.5 wt. % and about 5 wt. %, and in still other embodiments in a rangebetween about 0.5 wt. % and about 1 wt % based on weight of polyether inthe organic solution. In certain other embodiments of the invention theamount of water added is in a range between about 0.3 wt. % and about 3wt. % based on weight of polyether in the organic solution. Thetemperature of the organic phase in contact with water may be raised toa temperature in some embodiments between the boiling point of water andthe boiling point of the organic phase under the prevailing pressure, inother embodiments to at least about 100° C., in still other embodimentsto a temperature between about 110° C. and the boiling point of theorganic phase and in still other embodiments to a temperature betweenabout 120° C. and the boiling point of the organic phase under theprocess conditions. Alternatively, the polymer-containing mixture incontact with water can be heated under partial vacuum, in which case thetemperature may also be less than 100° C. as well as in the ranges givenabove. Under these conditions water generates small bubbles of steamthat escape the organic phase and evaporate. Any organic solvent thatescapes with the steam may be recovered using conventional means.Although the invention is not limited by any theory of operation, it isbelieved that in the process of water evaporation species dissolved inthe aqueous phase recrystallize, grow in size, and form agglomerates sothat they may sediment to the bottom of the tank when stirring isstopped. Typically any alkali metal halide recrystallizes duringevaporation of water to form agglomerates. Said agglomerates aretypically larger in size than any crystallites or agglomerates that maybe present before an evaporation step. Essentially all or at least aportion of alkali metal halide is now typically in a form that can beseparated (such as by filtration or decantation) following applicationof heat. The polyether-containing mixture is typically held at atemperature in the desired range until at least some of or most of oressentially all of the water has evaporated, or in some embodimentsuntil essentially all or at least a portion of alkali metal halide is ina form that can be separated. The mixture may now be subjected to asolid separation step such as filtration or decantation. An organicpermeate from filtration may be subjected to further purification stepsand/or sent to equipment for recovery of polymer. A filter cake itselfmay be treated to recover any entrained polymer and other valuablespecies by standard techniques, such as by extracting with organicsolvent.

[0076] In a particular embodiment a polymer mixture comprises (i) anaromatic polyetherimide, (ii) hexaethylguanidinium chloride catalyst,(iii) sodium chloride, and (iv) o-dichlorobenzene. Water is provided inthe prescribed amounts and the temperature of the ODCB phase is raisedto a temperature in some embodiments between the boiling point of waterand the boiling point of ODCB under the prevailing pressure, in otherembodiments to at least 110° C., in still other embodiments to atemperature between about 110° C. and the boiling point of ODCB underthe process conditions and in still other embodiments to a temperaturebetween about 120° C. and the boiling point of ODCB under the processconditions (wherein the normal boiling point of ODCB is 180° C. at oneatmosphere pressure). Alternatively, the polymer-containing mixture canbe heated under partial vacuum, in which case the temperature may alsobe less than 110° C. as well as in the ranges given above. Any ODCB thatescapes with the steam may be recovered using conventional means. In theprocess of water evaporation sodium chloride dissolved in the aqueousphase may recrystallize, and the crystallites grow in size, and formagglomerates so that they may sediment to the bottom of the tank whenstirring is stopped. For instance, the initial size of sodium chloridecrystals produced during a typical polyetherimide polymerization maytypically be in the range of about 0.5 to about 20 μm in diameter in anODCB phase. The agglomerates are typically larger in size than anycrystallites or agglomerates that may be present before an evaporationstep. A portion of residual sodium chloride is now typically in a formthat can be filtered. The polymer mixture is filtered using knownmethods. The ODCB permeate from filtration may be subjected to furtherpurification steps and/or sent to equipment for recovery ofpolyetherimide from organic solvent. The filter cake itself may betreated to recover any entrained polyetherimide and other valuablespecies by standard techniques, such as by extracting with ODCB.

[0077] Water may be provided to a polyether-containing mixture by anyconvenient method. In one embodiment at least one filtration step may beincluded following one or more water extraction steps in which casewater is provided as residual water remaining after extraction.Additional water may be added if desired. This embodiment may beemployed, for example, in embodiments for polyether-containing mixturesin which the initial particle size of solids present in the organicphase may be such that filtration prior to extraction is not feasible orcost effective. The combination of one or more water extraction stepsfollowed by a filtration step may be used to treat polyether/organicsolvent mixture, or rag layers therefrom, or the combination ofpolyether/organic solvent mixture and rag layer. Thus, in a particularembodiment a polyetherimide/ODCB reaction mixture comprising sodiumchloride, residual monomer, and catalyst is subjected to one or morewater extraction steps to remove the bulk of water-soluble species, andthen subjected to at least one filtration step comprising heating thereaction mixture as described.

[0078] In other embodiments a polyether-containing solution may betreated with water to effect agglomeration of alkali metal halide asdescribed. Following removal of solid alkali metal halide by a suitablesolid separation step, the polyether-containing solution may beextracted with water as previously described to effect removal ofremaining water-soluble species such as ionic catalysts and catalystdecomposition products. A distribution coefficient (K_(d)) of catalystbetween water and organic phases (as represented by the ratio of theconcentration of catalyst in the aqueous phase to the concentration ofcatalyst in the organic phase) is in some embodiments at least 1, and inother embodiments in a range of between about 1 and about 60. Thedistribution coefficient may be affected by such variables as the ratioof aqueous phase to organic phase, the time and intensity of stirring,the concentration of alkali metal halide, and the temperature amongother factors. Recovery of water-soluble species such as catalystspecies may be effected using known methods such as by removing water bydistillation in the presence of organic solvent until substantially allthe water is removed. The distillation may be further continued until adesired concentration of catalyst in organic solvent and a desiredresidual water level are obtained. If necessary, additional organicsolvent may be added to the distillation residue as required.

[0079] In another embodiment the method of the present inventioncomprises initial treatment of a polyether-containing mixture by atleast one non-aqueous or dry filtration step, in which contaminatingspecies are removed as solid particles or adsorbed species in thesubstantial absence of water. Substantial absence of water in thepresent context means that the organic solution contains in someembodiments less than about 1%, in other embodiments less than about0.5%, in still other embodiments less than about 0.2%, in still otherembodiments less than about 0.1%, and in still other embodiments lessthan about 0.01% by weight water. In some embodiments dry filtration isperformed before any step comprising treatment of the polymer-containingsolution with water, so that only adventitious water may be present inthe polymer-containing solution. Typical species which may be removed bydry filtration include alkali metal halide and residual monomer salts.Dry filtration may be performed using standard filtration methods,including those which employ one or more steps of mechanical filtrationof solid particles, separation using liquid-solid cyclone separators,ion-exchange adsorption (for example, to recover catalyst), or vacuumconveyor belt separation.

[0080] In a particular embodiment polyetherimide-containing ODCBmixtures are treated by filtration to remove such filterable species assodium chloride and bisphenol A monomer species as solid particles fromthe ODCB phase without initially adding water. Other insoluble specieswill also be removed from the ODCB phase. Following filtration, catalystspecies and other non-filterable, water-soluble species may be separatedand recovered via aqueous methods such as those employing a dynamic orstatic mixer or any of the aqueous configurations previously discussed.In one embodiment acid quenching is postponed until after filtration sothat bisphenol A salts can be removed by filtration; otherwise,bisphenol A formed during quenching may become soluble in the organicphase and may not be efficiently removed by solids filtration. Inanother embodiment quenching may be done before filtration, for exampleif bisphenol A salts are not present. The permeate from the filtrationstep is typically a clean solution of polymer and catalyst in ODCB. Thestream that is rejected by the filter is typically a concentrated slurryof sodium chloride, residual monomer species, and some catalyst in ODCB.The primary filter may be at least one of either a dead-end filter or across-flow filter. If a dead-end filter is used, a back-washing step isrequired to remove the solids from the filter. Since flux through adead-end filter is indirectly proportional to viscosity, decreasing thesolution viscosity will typically increase the flux by a proportionatefactor. The viscosity is largely determined by temperature and polymerconcentration. Therefore, increasing the temperature or decreasing thepolymer concentration may typically result in increased flux through afilter. In particular embodiments a polyetherimide solution in ODCB at aconcentration in a range of in one embodiment between about 5 wt. % andabout 25 wt. %, and in another embodiment in a range of between about 10wt. % and about 15 wt. %, may be conveniently filtered at a temperatureup to about the boiling point of ODCB, and in other particularembodiments at a temperature of about 90-180° C.

[0081] If a cross-flow filter is used, nearly continuous operation ispossible but at least one secondary filter is typically required tominimize product loss. Process time and costs will determine whichfiltration method is best. If needed, the secondary filter canconcentrate the slurry to a cake. The secondary filter may be a dead-endfilter (such as a candle filter or a belt press) or a liquid cyclone. Aliquid cyclone can perform the separation because the concentration ofparticles that occurs during cross-flow filtration induces solidparticles to agglomerate and the inertial forces that promote separationin a liquid cyclone are often more effective for separation of largeragglomerates.

[0082] The permeate stream (from both the primary and, if necessary, thesecondary filters) that is particle-free can be quenched with acid andsent for catalyst recovery. Because catalyst is typically more solublein water than in ODCB, this stream can be processed with any of theaqueous methods described above. Similarly, catalyst can be processedvia the dry method of ion exchange described hereinafter. Again,multiple combinations of aqueous and dry purification configurations arepossible, depending on the relative process conditions and the desiredlevel of purification.

[0083] In still another embodiment the method of the invention comprisesat least one dry filtration step in the presence of a solid adsorptionmedium that may adsorb or absorb soluble species from apolyether-containing mixture. Insoluble species such as an alkali metalhalide may be removed by simple physical filtration n the same process.The mechanism of adherence to a solid adsorption medium is not importantprovided that the medium serves to remove selected species in one ormore filtration steps while passing essentially all polyether and anyother species not selected. The adsorption medium may be contacted withthe polymer-containing mixture either by addition of all or a portion ofthe medium to the mixture followed by stirring, in one embodiment in arange of between about room temperature and about the boiling point ofthe organic phase under the prevailing conditions, in other embodimentsin a range of between about 25° C. and about 220° C., in otherembodiments in a range of between about 25° C. and about 180° C., inother embodiments in a range of between about 60° C. and about 180° C.,in other embodiments in a range of between about 80° C. and about 160°C., in other embodiments in a range of between about 80° C. and about140° C., in other embodiments in a range of between about 85° C. andabout 120° C., in other embodiments in a range of between about 85° C.and about 110° C., and in other embodiments in a range of between about90° C. and about 105° C. In particular embodiments the adsorption mediummay be contacted with the polymer-containing mixture either by additionof all or a portion of the medium to the mixture followed by stirring,at a temperature in one embodiment in a range of about 25-120° C., andin other embodiments in a range of about 60-105° C. In other embodimentsthe heated mixture can be filtered through all or a portion ofadsorption medium not previously contacted with the mixture. In someembodiments the polymer-containing solution is quenched with acid beforedry filtration.

[0084] Suitable adsorption media include, but are not limited to,alumina, silica, clay, montmorillonite, zeolite, charcoal, diatomaceousearth, fuller's earth, commercial filter agents such as CELITE, andother media typically employed in adsorption chromatography. In generalhigher surface area adsorbents (for example as represented by highermesh numbers relating to smaller particle size) are more efficient inadsorbing the desired species. In a particular embodiment apolyetherimide reaction mixture in ODCB may be contacted with anappropriate adsorption medium to adsorb essentially all or a portion ofsoluble species (other than polyetherimide) such as ionic catalystspecies, such as hexaethylguanidinium chloride. In a particularembodiment the adsorption medium is silica. The treated mixture can thenbe filtered one or more times to remove essentially all or a portion ofinsoluble alkali metal halide (such as sodium chloride) and adsorbedcatalyst species on the medium. In alternative embodiments substantiallyall or at least a portion of alkali metal halide (such as sodiumchloride) may be removed before treatment of the polymer-containingsolution with a solid adsorption medium. In the present contextsubstantially all the alkali metal halide means greater than about 90wt. % alkali metal halide.

[0085] Following filtration (or other suitable solid separation step),catalyst species may be recovered from the solid medium using methodsknown in the art, and any non-polyether, soluble species, if stillpresent in the filtrate, may be separated and recovered, for example byfurther filtration steps or by aqueous methods such as those employing adynamic or static mixer or any of the aqueous configurations previouslydiscussed. In some embodiments the adsorption medium may be regeneratedfor further use using known methods, for example by treatment with anorganic acid such as acetic acid, or an inorganic acid such ashydrochloric acid, hydrobromic acid, phosphoric acid, or phosphorousacid.

[0086] In still another embodiment the method of the present inventioncomprises at least one dry filtration step followed by at least one ionexchange step for catalyst recovery. The dry filtration step may beaccomplished by any combination of filtration methods describedhereinabove. For the second step, ion exchange on a resin bed can beused after filtration to reclaim cationic catalyst remaining in theorganic phase. Following ion exchange, the process solution may be sentfor further purification and/or to an isolation step for polyetherrecovery by standard methods.

[0087] A purification process comprising any combination of at least onedry filtration step followed by at least one ion exchange step may beemployed. In one embodiment the polyether-containing mixture is notquenched with acid before at least one dry filtration step and at leastone ion exchange step. In this case the polymer-containing mixturefollowing at least one filtration step may be contacted at least oncewith an ion exchange resin in the sodium form to remove ionic catalystand release sodium chloride. In an alternative embodiment an unquenchedpolymer-containing mixture is contacted at least once with ion exchangeresin in the hydrogen form and the resin itself serves entirely or atleast partially as an acid quencher for the polymer-containing mixture,adsorbing ionic catalyst in the process. In another embodiment thepolymer-containing mixture is quenched with acid after at least one dryfiltration step. In this case the mixture following at least onefiltration step and acid quenching may be contacted at least once withan ion exchange resin in the hydrogen form to remove ionic catalyst andrelease hydrogen chloride. In a particular embodiment a polyetherimidereaction mixture containing hexaalkylguanidinium chloride catalyst inODCB, after at least one filtration step and acid quenching, iscontacted at least once with an ion exchange resin in the sodium form.

[0088] A packed column of ion exchange resin can be used to exchangeionic catalyst for recovery. The identity of the ion exchange resin isnot critical so long as the ion exchange resin is effective forrecovering cationic catalyst for the polymer-containing mixture.AMBERLYST 36 or AMBERLYST 15 resins available from Rohm and Haas Co. canbe used for this purpose. In a particular embodiment apolyetherimide-containing ODCB reaction mixture is passed through aresin bed operated below about 90° C. Depending on the mode ofoperation, the resin column will adsorb the catalyst cation andtypically release sodium chloride or hydrochloric acid.

[0089] The ion exchange process may be performed in a batch,semi-continuous, or continuous mode. In one embodiment a columnsaturated with catalyst cation is regenerated off-line withhydrochloride acid and the catalyst chloride salt is recovered from theaqueous phase for reuse. While a saturated column is being regenerated,at least one fresh column may be in use for recovering catalyst cationfrom further process solution.

[0090] Following any of the purification procedures illustratedhereinabove, a polyether-containing organic solution may be sent to apolymer isolation step where the polyether may be isolated free oforganic solvent by standard methods, such as by anti-solventprecipitation, filtration, and drying, or by devolatilization, forexample, in an appropriate extruder with recovery and recycling of theorganic solvent. In a particular embodiment a polyetherimide is isolatedfrom an ODCB solution and the ODCB is recovered and recycled for furtheruse. The isolated polyetherimide preferably contains as low a sodiumlevel as possible, in one embodiment less than about 100 ppm sodium, inanother embodiment less than about 50 ppm sodium, in still anotherembodiment less than about 25 ppm sodium, in still another embodimentless than about 10 ppm sodium, and in still another embodiment less thanabout 7 ppm. A particular polyetherimide comprises the reaction productof a bisphenol A moiety, particularly bisphenol A disodium salt, with atleast one of 1,4- or 1,3-bis[N-(4-chlorophthalimido)]benzene.

[0091] Without further elaboration, it is believed that one skilled inthe art can, using the description herein, utilize the present inventionto its fullest extent. The following examples are included to provideadditional guidance to those skilled in the art in practicing theclaimed invention. The examples provided are merely representative ofthe work that contributes to the teaching of the present application.Accordingly, these examples are not intended to limit the invention, asdefined in the appended claims, in any manner. The terms “extraction”and “wash” are used interchangeably.

EXAMPLE 1

[0092] A polyetherimide was prepared in o-dichlorobenzene through thereaction of bisphenol A disodium salt and1,3-bis[N-4-chlorophthalimido]benzene in the presence ofhexaethylguanidinium chloride catalyst (HEG). The polymer-containingmixture was quenched at 120° C. with glacial acetic acid and diluted toabout 15% solids (wt. polymer/wt. polymer+wt. solvent) through additionof more o-dichlorobenzene. The mixture (about 10 liters; about 13kilograms) was washed with about 4.1 kilograms water (3:1organic:aqueous) at a temperature of about 85-90° C. and fed to aliquid/liquid continuous centrifuge at about 90° C. at different rates.All of the organic phase was collected and washed with a second portionof water (about 4.1 kilograms), and the organic phase fed to thecentrifuge a second time. All of the organic phase was collected andwashed with a third portion of water (about 4.1 kilograms), and theorganic phase fed to the centrifuge a third time. For each set ofconditions the organic phase was analyzed by ion chromatography forsodium, HEG and PEG (pentaethylguanidinium chloride, a decompositionproduct of HEG); duplicate analyses were run on the same sample.Conditions and analyses are summarized in Table 1. In each case the dataare reported vs. polymer rather than vs. the entire mixture. Thecentrifuge employed had a maximum rating of 10,000 rpm. TABLE 1 Cen-Sodium HEG PEG Org. + Aq. tri- analyses, analyses, analyses, Flow fugeppm ppm vs. ppm vs. Run No.* grams/minute rpm vs. polymer polymerpolymer first pass 1000   75% 890/905 333/335 150/150 first pass 900100% 690/712 327/322 141/142 first pass 450 100% 769/828 292/293 134/132first pass 600 100% 785/809 290/288 131/131 second 800 100% 251/31031/32 19/21 pass second 400 100% 224/192 38/41 24/25 pass third pass 800100% 165/177 9/8 6/5

[0093] The data show that the sodium and catalyst level decreases witheach successive wash. The sodium level may be further decreased usingevaporation and filtration process steps.

EXAMPLE 2

[0094] The same quenched, diluted polyetherimide-containing mixture usedin Example 1 (4 liters) was fed simultaneously along with water througha concentric tube assembly to a homogenizer at flow rates of 450 gramsper minute for the organic phase and 150 grams per minute for theaqueous phase. Both the organic and aqueous phases were at a temperatureof about 85-90° C. The homogenizer, comprising a rotor assembly withblades and a stator with outlet orifices on the periphery and an exitport leading to a centrifuge, was operated at different rpms. Thehomogenized mixture from the homogenizer was fed directly to aliquid/liquid centrifuge operated at 100% rpm capability. All of theorganic phase was collected and fed to the homogenizer along with waterunder the same conditions as for the first pass, and the output fed tothe centrifuge a second time. All of the organic phase was collected andfed to the homogenizer along with water under the same conditions as forthe first pass, and the output fed to the centrifuge a third time. Foreach set of conditions the organic phase was analyzed by ionchromatography for sodium, HEG and PEG (pentaethylguanidinium chloride,a decomposition product of HEG); duplicate analyses were run on the samesample. Conditions and analyses are summarized in Table 2. In each casethe data are reported vs. polymer rather than vs. the entire mixture.TABLE 2 Sodium HEG PEG analyses, Homogenizer analyses, ppm analyses, ppmppm vs. Run No.* rpm vs. polymer vs. polymer polymer first pass 15001592/1583 242/239 81/80 first pass 3000 2306/2320 261/261 100/99 firstpass 4000 2010/1996 182/188 77/77 second pass 2000 670/682 15/15 9/9third pass 1500 129/125 8/9 4/4

[0095] The data show that the sodium level decreases with eachsuccessive wash. The sodium level may be further decreased usingevaporation and filtration process steps.

EXAMPLE 3

[0096] A similar polyetherimide-containing mixture to that used inExample 1 was held in a 10 gallon reactor, quenched at about 120° C.with glacial acetic acid, and diluted to about 8% solids (wt.polymer/wt. polymer+wt. solvent) through addition of moreo-dichlorobenzene. The mixture was transferred to clean containers andthe reactor rinsed with a small amount of o-dichlorobenzene anddeionized water to remove any salts that might have adhered to the wallsof the reactor. The polymer-containing mixture was returned to therinsed reactor and heated to 80° C. The mixture was then extracted threetimes, each time with nine liters deionized water also at 80° C. Thephases were mixed each time for ten minutes with gentle agitation. Thefirst two washes were allowed to settle for one hour, and the third washwas allowed to settle for two days at 80° C. For each set of conditionsthe organic phase was analyzed for sodium by ion chromatography. Thesodium content after the first wash was 797 ppm; after the second wash,223 ppm; and after the third wash, 32 ppm vs. polymer.

EXAMPLE 4

[0097] An acid-quenched polyetherimide-containing mixture similar tothat used in Example 1 (except diluted to 10% solids) was treated withwater to agglomerate salt and filtered. The polyetherimide-containingsolution was pumped into a vessel containing water which had beenpreheated to 90° C. The amount of water was 7750 millilitersrepresenting a 1:6 wt./wt. ratio versus the 10% polymer solution. Thephases were mixed by stirring at 100-200 rpm for 1-5 minutes, afterwhich stirring was stopped and the mixture allowed to separate forvarious times at 90° C. The organic phase was separated and the washprocess repeated various numbers of times. No rag layers were observedin the wash processes. Table 3 shows the results of analyses on theorganic phase. Sodium was analyzed by ion selective electrode, and HEGand PEG were analyzed by ion chromatography. TABLE 3 HEG analyses, PEGanalyses, Analyses Sodium analyses, ppm vs. ppm vs. condition ppm vs.polymer polymer polymer supernatant — 2210 586 polymer solution aftersteelwool 1016 — — filtration after cartridge 26 2002 533 filtration1^(st) wash/ 13 313 121 12 hrs. 2^(nd) wash/ 13 206 84 2.5 hrs. 3^(d)wash/ 3 154 63 36 hrs.

EXAMPLE 5

[0098] The conditions of example 4 were repeated except that the amountof water used was 40 liters representing a 1:1.7 wt./wt. ratio versusthe 10% polymer solution. The organic phase was separated and the washprocess repeated various numbers of times. No rag layers were observedin the wash processes. Table 4 shows the results of analyses on theorganic phase. TABLE 4 HEG analyses, PEG analyses, Sodium analyses, ppmvs. ppm vs. Analyses condition ppm vs. polymer polymer polymer afteracid quench — 2833 474 after bag filter 48  2621 461 after cartridge 02556 445 filtration 1^(st) wash/12 hrs. 0 116 27 2^(nd) wash/2 hrs. — 00

EXAMPLE 6

[0099] The conditions of example 4 were repeated except that the amountof water used was 40 liters representing a 1:1.7 wt./wt. ratio versusthe 10% polymer solution. The organic phase was separated and the washprocess repeated various numbers of times. No rag layers were observedin the wash processes. Table 5 shows the results of analyses on theorganic phase. TABLE 5 HEG analyses, PEG analyses, Sodium analyses, ppmvs. ppm vs. Analyses condition ppm vs. polymer polymer polymer after bagfilter 437 2803 537 after cartridge 0 2686 515 filtration 1^(st) wash/12 hrs. 8 100 15 2^(nd) wash/2 hrs. 0 0 0

EXAMPLE 7

[0100] The conditions of example 4 were repeated except that the amountof water used was 317 liters representing a 1:2 wt./wt. ratio versus the10% polymer solution. The organic phase was separated and the washprocess repeated various numbers of times. No rag layers were observedin the wash processes. Table 6 shows the results of analyses on theorganic phase. TABLE 6 HEG analyses, PEG analyses, Sodium analyses, ppmvs. ppm vs. Analyses condition ppm vs. polymer polymer polymer afteracid quench — 2592   371 after bag filter 11*  2026*   326* 1^(st) wash0* 187*   42* 2^(nd) wash 0* 68*   8*

EXAMPLE 8

[0101] A solution of 90 grams ortho-dichlorobenzene was heated to 150°C. in a 250 milliliter (ml) round-bottom, three neck flask equipped witha condenser and an overhead stirrer. To the solution was added 10 gramsof a polyetherimide over 20 minutes with stirring. The polyetherimidecomprised structural units derived from bisphenol A and1,3-bis[N-4-chlorophthalimido]benzene. The polymer was allowed todissolve completely over 3 hours. The temperature of polymer solutionwas reduced to 95° C. To this polymer solution was added 50 ml ofboiling deionized water and the internal temperature was maintained at95° C. The solution was stirred at 220 rpm for 2 minutes and thenstirring was discontinued. Within 4 minutes the phases separatedcompletely. The solution was then stirred at 220 rpm for 1 hour afterwhich stirring was discontinued. The separation of the two phases wasvery slow. After two hours a transparent aqueous layer was obtained witha polymer film on top of the aqueous layer. The predominantly organicphase was still emulsified. On standing overnight the emulsion did notseem to break.

[0102] The transparent aqueous phase was separated and the organic phasecontaining emulsion was heated under stirring to distill off water. Theorganic phase was finally heated to increase the temperature to 140° C.during which time the polymer solution became clear again. The solutionwas then cooled to 95° C. Stirring was discontinued and 50 ml of boilingdeionized water was added to the solution. The mixture was stirred forthree minutes and then the stirring was discontinued. The two phasesseparated immediately into transparent phases. This demonstrates thatheat treatment is beneficial to phase separation in subsequent waterwashes.

EXAMPLE 9

[0103] A polyetherimide was prepared in o-dichlorobenzene through thereaction of bisphenol A disodium salt and1,3-bis[N-4-chlorophthalimido]benzene in the presence ofhexaethylguanidinium chloride catalyst (HEG). The acid-quenched polymersolution was diluted with ortho-dichlorobenzene to 10% polymer solution,and 881 grams of solution was placed in a 2 liter vessel fitted with anoverhead condenser, a thermometer, a nitrogen inlet, an extra port foraddition of reagents and a bottom drain valve. The solution was heatedto 95° C. and 432 grams of deionized water was added maintaining thetemperature of the mixture in a range of about 93-96° C. The solutionwas stirred for 15 minutes at 170 rpm after which stirring wasdiscontinued. Separation of the phases was complete in two hours. Theorganic layer was turbid and most of the rag material came in theorganic phase. Polymer film formed at the top of aqueous layer. The twophases were well separated at the boundary.

[0104] The two layers were separated through bottom drain valve, and theorganic phase was transferred back to the vessel. The organic phase washeated and the temperature raised to 142° C. when the solution becametransparent barring a few floating polymer particles. On cooling thesolution became slightly more hazy with more particles seen but muchless than after the first wash. When the temperature reached 104° C.,445 ml hot deionized water (93-96° C.) was added. When the temperatureof the wash reach 95° C., stirring was started. Slow azeotropic removalof water and ortho-dichlorobenzene was observed. Stirring was continuedfor 15 minutes at 120 rpm and then stopped. Clear separation wasobserved between the phases in 10 minutes. The temperature of themixture was maintained between about 87° C. and about 90° C. for onehour. There was a thin polymer layer on top of aqueous layer, theaqueous layer was clear, and the organic layer was slightly turbid.There was practically no rag layer. The two layers could be separatedvery easily.

[0105] The organic phase was transferred back to the vessel and thetemperature was raised to 138° C. There were some polymer particles seenin the organic phase, but the amount was less. The temperature of thesolution was reduced to 105° C. and 432 grams hot deionized water(93-96° C.) was added. The temperature of the mixture was reduced to 87°C. and the mixture was stirred at 170 rpm for 15 minutes. Someazeotropic removal of water and ortho-dichlorobenzene was observed.Stirring was stopped and the mixture was allowed stand. Phase separationtook place more slowly than in the second wash but there was only a verysmall rag layer at the end of one hour. A thin layer of polymer was seenon top of the aqueous layer. The organic layer was slightly turbid butthe two layers could be easily separated. This demonstrates that heattreatment is beneficial to phase separation in subsequent water washes.

EXAMPLE 10

[0106] Four washing experiments were performed on a polyetherimidesolution similar to that from the previous example by stirring for 15minutes followed by settling time of 30 minutes. Between each washingstep the temperature of the organic phase was raised to 135-140° C. Thewashings were done typically at 90° C. Little or no emulsion formationwas observed and the separation of phases was fairly easy as in Example9.

EXAMPLE 11

[0107] A polyetherimide-containing mixture similar to that used inExample 1 and containing about 800 ppm soluble ionic chloride in theform of hexaethylguanidinium chloride was quenched at about 43° C. withanhydrous hydrochloric acid, and diluted to about 5% solids (wt.polymer/wt. polymer+wt. solvent) through addition of moreo-dichlorobenzene. The mixture was treated with silica gel (60-200 mesh;0.5 grams per 10 g. of polymer in solution) and stirred at 60° C. Themixture was filtered and the filtrate analyzed for soluble ionicchloride by titration. The soluble ionic chloride value was 75 ppm basedon polyetherimide.

EXAMPLE 12

[0108] An acid-quenched polyetherimide-containing mixture similar tothat used in Example 1 (except diluted to 10% solids) was treated withwater to agglomerate salt and filtered. The polymer-containing filtratewas treated with 0.37 wt. % (based on polymer solution) silica gel at90° C., and stirred for 6.5 hours at 100-200 rpm. Samples were takenperiodically for analysis. After 5.5 hours additional silica gel wasadded to bring the total amount to 0.7 wt. %. Sodium was analyzed by ionselective electrode, and HEG and PEG were analyzed by ionchromatography. Analyses are summarized in Table 7. HEG analyses, PEGanalyses, Analyses ppm vs. ppm vs. condition polymer polymer 1 hr. 142334 2 hr. 131 49 5.5 hr.   124 57 6.5 hr.   0 0

EXAMPLE 13

[0109] An acid-quenched polyetherimide-containing mixture similar tothat used in Example 1 (except diluted to 10% solids) was treated withwater to agglomerate salt and filtered. The polymer-containing filtrate(70.9 kilograms) was treated with 500 grams silica gel (60-200 mesh) at90° C., and stirred at 400 rpm. Samples were taken periodically foranalysis. Analyses are summarized in Table 8. TABLE 8 Na analyses, HEGanalyses, PEG analyses, Analyses ppm vs. ppm vs. ppm vs. conditionpolymer polymer polymer after acid — 2592 371 quench after filtration11*  2026*  326* after 1 hr. with —   0  0 silica gel

[0110] *average of two values

EXAMPLE 14

[0111] An acid-quenched polyetherimide-containing mixture similar tothat used in Example 1 (except diluted to 10% solids) was treated withwater to agglomerate salt and filtered. About 90 grams ofpolyetherimide-containing solution was filtered at 90° C. a second timethrough a 10 micrometer pore size polytetrafluoroethylene membrane whichhad been loaded with 5 grams of silica gel (60-200 mesh). Filtration wasrepeated twice more at 90° C. through the same silica gel on themembrane. Analyses are summarized in Table 9. TABLE 9 HEG analyses, PEGanalyses, Analyses ppm vs. ppm vs. condition polymer polymer beforefiltration 2227 614 after 1^(st) filtration 246 200 after 2nd filtration119 97

EXAMPLE 15

[0112] An acid-quenched polyetherimide-containing mixture similar tothat used in Example 1 (except diluted to 10% solids) was treated withwater to agglomerate salt but not filtered. About 75 grams ofpolyetherimide-containing solution was filtered at 90° C. through a 10micrometer pore size polytetrafluoroethylene membrane which had beenloaded with 10 grams of silica gel (60-200 mesh). Sodium was analyzed byion selective electrode, and HEG and PEG were analyzed by ionchromatography. The filtered polymer solution contained no detectableHEG or PEG species and no detectable sodium ion by analysis.

EXAMPLE 16

[0113] An acid-quenched polyetherimide-containing mixture similar tothat used in Example 1 (except at 10% solids) was treated with water toagglomerate salt and filtered. The polymer-containing filtrate (150grams)was treated with 0.5 grams silica gel (60-200 mesh) at 90° C., andstirred at 250 rpm for 15 minutes. The mixture was then filtered througha 10 micrometer pore size membrane. Samples were analyzed as summarizedin Table 10. TABLE 10 Na analyses, HEG analyses, PEG analyses, Analysesppm vs. ppm vs. ppm vs. condition polymer polymer polymer before silica2.5 1640 282 gel treatment after membrane — 0 0 filtration

EXAMPLE 17

[0114] An acid-quenched polyetherimide-containing mixture similar tothat used in Example 1 (except at 10% solids) was treated with water toagglomerate salt and filtered. The polymer-containing filtrate (150grams)was treated with 5.0 grams silica gel (60-200 mesh) at 90° C., andstirred at 250 rpm for 5 minutes. The mixture was then filtered througha 10 micrometer pore size membrane. Samples were analyzed as summarizedin Table 11. TABLE 11 Na analyses, HEG analyses, PEG analyses, Analysesppm vs. ppm vs. ppm vs. condition polymer polymer polymer before silicagel 6 833 372 treatment after membrane — 0 0 filtration

EXAMPLE 18

[0115] An acid-quenched polyetherimide-containing mixture similar tothat used in Example 1 at 15% solids was treated with water toagglomerate salt and filtered. Samples of the polymer-containingfiltrate (100 grams) were treated with 0.05 grams silica gel (60-200mesh) at 90° C., and stirred at 250 rpm for various times. Each mixturewas then filtered through a 10 micrometer pore size membrane. Analyseson samples after silica gel treatment and membrane filtration aresummarized in Table 12. Before silica gel treatment the solution showed0 ppm sodium, 445 ppm HEG, and 230 ppm PEG. TABLE 12 HEG analyses, PEGanalyses, Stirring time, ppm vs. ppm vs. minutes polymer polymer 5 337191 15 267 174 30 291 179

EXAMPLE 19

[0116] An acid-quenched polyetherimide-containing mixture similar tothat used in Example 1 at 15% solids was treated with water toagglomerate salt and filtered. Samples of the polymer-containingfiltrate (100 grams) were treated with various amounts of silica gel(60-200 mesh, unless noted) at 90° C., and stirred at 250 rpm for 5minutes. Each mixture was then filtered through a 10 micrometer poresize membrane. Analyses on samples after silica gel treatment andmembrane filtration are summarized in Table 13. Before silica geltreatment the solution showed 0 ppm sodium, 2256 ppm HEG, and 445 ppmPEG. TABLE 13 Silica gel HEG analyses, PEG analyses, amount, ppm vs. ppmvs. grams polymer polymer 0.10 1965 389 0.05 2208 408 0.05* 2524 4670.20 1423 318 0.30 1009 248 0.40 724 184

[0117] *silica gel mesh size 28-200

EXAMPLE 20

[0118] An acid-quenched polyetherimide-containing mixture similar tothat used in Example 1 at 15% solids was treated with water toagglomerate salt and filtered. Samples of the polymer-containingfiltrate (100 grams) were treated with various amounts of silica gel(60-200 mesh, unless noted) at 90° C., and stirred at 250 rpm for 5minutes. Each mixture was then filtered through a 10 micrometer poresize membrane. Analyses on samples after silica gel treatment andmembrane filtration are summarized in Table 14. Before silica geltreatment the solution showed 0 ppm sodium, 821 ppm HEG, and 377 ppmPEG. TABLE 14 Silica gel Stirring HEG analyses, PEG analyses, amount,time, ppm vs. ppm vs. grams minutes polymer polymer 0.50 5 164 133 0.50*15 5 5 0.20 15 108 40 0.20 10 220 140 0.50 10 36 5 0.20 5 296 163 0.0530 560 318

[0119] *silica gel mesh size 28-200

EXAMPLE 21

[0120] An acid-quenched polyetherimide-containing mixture similar tothat used in Example 1 at 10% solids was treated with water toagglomerate salt and filtered. Samples of the polymer-containingfiltrate were treated with various amounts of silica gel (60-200 mesh)at 90° C., and stirred at 250 rpm for various times. Each mixture wasthen filtered through a 10 micrometer pore size membrane. Analyses onsamples after silica gel treatment and membrane filtration aresummarized in Table 15. Before silica gel treatment the solution showed0 ppm sodium, 2686 ppm HEG, and 515 ppm PEG. TABLE 15 Silica gelStirring HEG analyses, PEG analyses, amount, time, ppm vs. ppm vs. gramsminutes polymer polymer 0.10 0.5 1257 369 0.10 1 1558 494 0.10 2 1001361 0.10 5 1044 343 0.10 16 1122 380 0.10 21 993 341 0.05 0.5 2041 4850.05 1 2287 548 0.05 5 1791 471 0.05 18 2035 501 0.05 23 2110 511 0.25 168 17 0.25 5 0 0 0.20 1 122 69 0.20 5 103 37 0.15 1 446 182 0.15 23.5435 169

EXAMPLE 22

[0121] A polyetherimide was prepared in o-dichlorobenzene through thereaction of bisphenol A disodium salt and1,3-bis[N-4-chlorophthalimido]benzene in the presence ofhexaethylguanidinium chloride catalyst (HEG). The polymer-containingmixture was quenched at a temperature between 150° C. and 180° C. withphosphoric acid and diluted to about 10% solids (wt. polymer/wt.polymer+wt. solvent) through addition of more o-dichlorobenzene. Thepolyetherimide-containing solution was treated at 90° C. with 300milliliters water (6.6 wt. % versus polyetherimide; 0.65 wt. % versus10% polyetherimide-containing solution) and stirred for 7 minutes at 112rpm, the 1 minute at 160 rpm. The mixture was allowed to settle for 15minutes at 90° C. then filtered once through steelwool and once througha 5 micrometer cartridge filter. Sodium was analyzed by ion selectiveelectrode, and HEG and PEG were analyzed by ion chromatography. Analysesare summarized in Table 16. TABLE 16 Na analyses, HEG analyses, PEGanalyses, Analyses ppm vs. ppm vs. ppm vs. condition polymer polymerpolymer supernatant — 2210 586 solution after steelwool 1016 — —filtration after cartridge   26* 2002 533 filtration

EXAMPLE 23

[0122] An acid-quenched polyetherimide-containing solution similar tothat in Example 22 was treated at 90° C. with 225 milliliters water (3.3wt. % versus polyetherimide; 0.32 wt. % versus 10%polyetherimide-containing solution) and stirred for 3 minutes at 92 rpm.The mixture was allowed to settle for 25 minutes at 90° C. then filteredonce through a 50 micrometer bag filter and once through a 5 micrometercartridge filter. Analyses are summarized in Table 17. TABLE 17 Naanalyses, HEG analyses, PEG analyses, Analyses ppm vs. ppm vs. ppm vs.condition polymer polymer polymer after acid — 2833 474 quench after bag48 2621 461 filtration after cartridge  0 2556 445 filtration

EXAMPLE 24

[0123] An acid-quenched polyetherimide-containing solution similar tothat in Example 22 was treated at 90° C. with 225 milliliters water (3.3wt. % versus polyetherimide; 0.33 wt. % versus 10%polyetherimide-containing solution) and stirred for 4 minutes at 93 rpm.The mixture was not allowed to settle. The water was removed bydistillation at about 180° C., after which the solution was filteredonce through a 100 micrometer bag filter and once through a 5 micrometercartridge filter. Analyses are summarized in Table 18. TABLE 18 Naanalyses, HEG analyses, PEG analyses, Analyses ppm vs. ppm vs. ppm vs.condition polymer polymer polymer after acid —  3328*  661* quench afterbag 437 2803 537 filtration after cartridge  0 2686 515 filtration

EXAMPLE 25

[0124] An acid-quenched polyetherimide-containing solution similar tothat in Example 22 was treated at 90° C. with 1765 milliliters water(3.3 wt. % versus polyetherimide; 0.32 wt. % versus 10%polyetherimide-containing solution) and stirred for 1 minute. Themixture was allowed to settle for 2 hours at 90° C. then filtered oncethrough a 25 micrometer bag filter. Analyses are summarized in Table 19.Na analyses, HEG analyses, PEG analyses, Analyses ppm vs. ppm vs. ppmvs. condition polymer polymer polymer after acid — 2592 371 quench afterbag 11*  2026*  326* filtration

EXAMPLE 26

[0125] A polyetherimide was prepared in o-dichlorobenzene through thereaction of bisphenol A disodium salt and1,3-bis[N-4-chlorophthalimido]benzene in the presence ofhexaethylguanidinium chloride catalyst (HEG). The polymer-containingmixture was quenched with phosphoric acid and diluted to about 10%solids (wt. polymer/wt. polymer+wt. solvent) through addition of moreo-dichlorobenzene. A portion of the polyetherimide-containing solutionwas treated at 90° C. with 5 milliliters water (3.3 wt. % versus 10%polyetherimide-containing solution) and stirred for 1 minute at 450 rpm.The water was removed by distillation at about 180° C., after which thesolution was filtered through a 5 micrometer cartridge filter to give anorganic solution containing 500 ppm sodium. The organic solution wasthen washed three times with 15-20 ml. water (with 0.5-1 hour settlingtime for each wash before separating the layers) to give an organicsolution containing 450 ppm sodium. Sodium was analyzed gravimetricallyas sodium chloride following ashing to remove other species.

EXAMPLE 27

[0126] An acid-quenched polyetherimide-containing solution as in Example26 was treated at 90° C. with 3 milliliters water (1.5 wt. % versus 10%polyetherimide-containing solution) and stirred for 1 minute at 450 rpm.After standing, the solution was decanted to give an organic solutioncontaining 90 ppm sodium, 2932 ppm PEG, and 453 ppm HEG. The organicsolution was then washed three times with 25 ml. water (with 1-2 hoursettling time for each wash before separating the layers) to give anorganic solution containing 46 ppm sodium, 19 ppm PEG, and 22 ppm HEG.Sodium was analyzed by ion selective electrode.

EXAMPLE 28

[0127] An acid-quenched polyetherimide-containing solution as in Example26 was treated at 90° C. with 3 milliliters water (1.5 wt. % versus 10%polyetherimide-containing solution) and stirred for 1 minute at 450 rpm.After standing, the solution was filtered under pressure through a 5micrometer cartridge filter to give an organic solution containing 4430ppm sodium, 3184 ppm HEG, and 330 ppm PEG. The organic solution was thenwashed three times with 25 ml. water (with 1 hour settling time for eachwash before separating the layers) to give an organic solutioncontaining 400 ppm sodium, 85 ppm HEG, and 5 ppm PEG. Sodium wasanalyzed by ion selective electrode.

EXAMPLE 29

[0128] An acid-quenched polyetherimide-containing solution as in Example26 was treated at 90° C. with 1 milliliter water (0.67 wt. % versus 10%polyetherimide-containing solution) and stirred for 1 minute at 450 rpm.The water was removed by distillation at about 180° C., after which thesolution was filtered through a 5 micrometer cartridge filter to give anorganic solution containing 9 ppm sodium, 2141 ppm HEG, and 502 ppm PEG(each an average of two values). The organic solution was then washedthree times with 25 ml. water (with 1 hour settling time for each washbefore separating the layers) to give an organic solution containing 0ppm sodium, 45 ppm HEG, and 7 ppm PEG. Sodium was analyzed by ionselective electrode.

EXAMPLE 30

[0129] An acid-quenched polyetherimide-containing solution as in Example26 was treated at 90° C. with 1 milliliter water (0.67 wt. % versus 10%polyetherimide-containing solution) and stirred for 1 minute at 450 rpm.The water was removed by distillation at about 180° C., after which thesolution was filtered through a 5 micrometer cartridge filter to give anorganic solution containing 8 ppm sodium, 2484 ppm HEG, and 676 ppm PEG(each an average of two values). The organic solution was then washedthree times with 25 ml. water (with 1 hour settling time for each washbefore separating the layers) to give an organic solution containing 0ppm sodium, 147 ppm BEG, and 46 ppm PEG. Sodium was analyzed by ionselective electrode.

EXAMPLE 31

[0130] An acid-quenched polyetherimide-containing solution as in Example26 was treated at 90° C. with 0.75 milliliters water (0.5 wt. % versus10% polyetherimide-containing solution) and stirred for 1 minute at 450rpm. The water was removed by distillation at about 180° C., after whichthe solution was filtered through a 5 micrometer cartridge filter togive an organic solution containing 0 ppm sodium, 1093 ppm HEG, and 217ppm PEG. The organic solution was then washed three times with 25 ml.water (with 1-3 hour settling time for each wash before separating thelayers) to give an organic solution containing 0 ppm sodium, 38 ppm HEG,and 8 ppm PEG. Sodium was analyzed by ion selective electrode.

EXAMPLE 32

[0131] A polyetherimide was prepared in o-dichlorobenzene through thereaction of bisphenol A disodium salt and1,3-bis[N-4-chlorophthalimido]benzene in the presence ofhexaethylguanidinium chloride catalyst (HEG). A 150 gram portion of thepolymer-containing mixture was quenched with 2 ml. acetic acid anddiluted to about 10% solids (wt. polymer/wt. polymer+wt. solvent)through addition of more o-dichlorobenzene. Thepolyetherimide-containing solution was treated at 90° C. with 0.5milliliters water and stirred for 1 minute at 450 rpm. The mixture wasfiltered to give an organic solution containing 42 ppm sodium, 2488 ppmHEG, and 245 ppm PEG. The organic solution was then washed three timeswith 20 ml. water (with 1-2 hour settling time for each wash beforeseparating the layers) to give an organic solution containing 14 ppmsodium, 798 ppm HEG, and 104 ppm PEG. Sodium was analyzed by ionselective electrode.

EXAMPLE 33

[0132] A 150 gram portion of the polymer-containing mixture as inExample 32 was quenched with acetic acid (0.5 wt. % based on polymersolution). The polyetherimide-containing solution was treated at 90° C.with 0.5 milliliters water and stirred for 1 minute at 450 rpm. Themixture was filtered to give an organic solution containing 0 ppmsodium, 3192 ppm HEG, and 589 ppm PEG. The organic solution was thenwashed three times with 20 ml. water (with 1.5-2 hour settling time foreach wash before separating the layers) to give an organic solutioncontaining 23 ppm sodium, 1303 ppm HEG, and 350 ppm PEG. Some emulsionformation was observed in each wash. Sodium was analyzed by ionselective electrode.

EXAMPLE 34

[0133] A polyetherimide was prepared in o-dichlorobenzene through thereaction of bisphenol A disodium salt and1,3-bis[N-4-chlorophthalimido]benzene in the presence ofhexaethylguanidinium chloride catalyst (HEG). A portion of acid-quenchedpolymer-containing mixture at 15% solids level was treated at 90° C.several times with various amounts of water each time stirring themixture for 3 minutes at 250 rpm. Table 20 shows the results of thewater extractions. Sodium was analyzed by ion selective electrode. TABLE20 Wash Settling Time Water phase recovered number (hours) Observations(vs. initial amount) 1 1.5 — 38 ml. (40 ml. initial) 2 12 emulsion 20ml. (40 ml. initial) 3 1 emulsion 37 ml. (40 ml. initial) 4 2 emulsion20 ml. (25 ml. initial) 5 2 emulsion 11 ml. (15 ml. initial)

[0134] After fifth wash, the organic solution contained 43 ppm sodium, 0ppm HEG, and 0 ppm PEG. The difference between the recovered and initialwater phase amounts shows the amount lost during emulsification.

EXAMPLE 35

[0135] The procedure of Example 34 was repeated except that thepolyetherimide-solution was at 10% solids level. Table 21 shows theresults of the water extractions. Sodium was analyzed gravimetrically assodium chloride by ashing. Little emulsion formation was observed in thewater washes. TABLE 21 Wash Settling Time Water phase recovered number(hours) (vs. initial amount) 1 2 28 ml. (30 ml. initial) 2 2 28 ml. (30ml. initial) 3 1.5 25 ml. (30 ml. initial) 4 1.5 27 ml. (30 ml. initial)

[0136] After the fourth wash, the organic solution contained 1380 ppmsodium.

EXAMPLE 36

[0137] The procedure of Example 34 was repeated except that thepolyetherimide-containing solution was filtered through a 10 micrometercartridge filter after the washes were completed. Table 22 shows theresults. Sodium was analyzed by ion selective electrode. TABLE 22 Waterphase Na HEG PEG Anal- Settling recovered analyses, analyses, analyses,yses Time (vs. initial ppm vs. ppm vs. ppm vs. after (hours) Observ.amount) polymer polymer polymer wash 1.5 — 34 ml. 14078* 266*  539* 1(45 ml. initial) wash 4 emul- 18 ml. — — — 2 sion (30 ml. initial) wash12 emul- 12 ml. 4853 90 186 3 sion (20 ml. initial) fil- — — —  170 104 183 tra- tion

EXAMPLE 37

[0138] The procedure of Example 36 was repeated except that thepolyetherimide-containing solution was at 10% solids level. Table 23shows the results. TABLE 23 Water phase Na HEG PEG Anal- Settlingrecovered analyses, analyses, analyses, yses Time (vs. initial ppm vs.ppm vs. ppm vs. after (hours) Observ. amount) polymer polymer polymerwash 1.5 — 38 ml. — 59 107 1 (45 ml. initial) wash 2 — 29 ml. — — — 2(30 ml. initial) wash 2 emul- 15 ml. 355  5  13 3 sion (20 ml. initial)fil- — — — 312  0  0 tra- tion

EXAMPLE 38

[0139] A polyetherimide was prepared in o-dichlorobenzene through thereaction of bisphenol A disodium salt and1,3-bis[N-4-chlorophthalimido]benzene in the presence ofhexaethylguanidinium chloride catalyst (HEG). A portion (100 grams) ofacid-quenched polymer-containing mixture at 15% solids level was treatedwith 3 milliliters of water and slowly stirred, after which the waterwas removed by distillation. The mixture was filtered through a 10micrometer pore size filter to remove agglomerated sodium chloride. Thefiltrate was stirred twice with water at 90° C. for 3 minutes at 250rpm. Table 24 shows the results. Sodium was analyzed by ion selectiveelectrode. TABLE 24 Water phase Na HEG PEG Anal- Settling recoveredanalyses, analyses, analyses, yses Time (vs. initial ppm vs. ppm vs. ppmvs. after (hours) Observ. amount) polymer polymer polymer fil- — — — 1075 269 tra- tion wash 2 emul- 25 ml. — — — 1 sion (30 ml. initial) wash2 emul-  9 ml. 11  3  28 2 sion (25 ml. initial)

[0140] While the invention has been illustrated and described in typicalembodiments, it is not intended to be limited to the details shown,since various modifications and substitutions can be made withoutdeparting in any way from the spirit of the present invention. As such,further modifications and equivalents of the invention herein disclosedmay occur to persons skilled in the art using no more than routineexperimentation, and all such modifications and equivalents are believedto be within the spirit and scope of the invention as defined by thefollowing claims. Although some particular embodiments of the inventionconcern methods for purification of a polyetherimide in an ODCBsolution, it is to be understood that the invention discloses methodswhich are suitable for the purification of any polyether made by ahalide displacement polymerization method in a water-immiscible solventwith boiling point at atmospheric pressure of greater than 110° C. and adensity ratio to water of greater than 1.1:1 at 20-25° C. All U.S.Patents cited herein are incorporated herein by reference.

What is claimed is:
 1. A method for purifying a mixture comprising (i)an aromatic polyether reaction product made by a halide displacementpolymerization process, (ii) a catalyst, (iii) an alkali metal halide,and (iv) a substantially water-immiscible organic solvent with boilingpoint at atmospheric pressure of greater than 110° C. and a densityratio to water of greater than 1.1:1 at 20-25° C., comprising the stepsof: (a) quenching the mixture with acid; and (b) at least one step ofcontacting a polyether-containing organic phase with water andseparating a water-containing phase from the organic phase, which stepcomprises using at least one of a liquid/liquid centrifuge, asolid/liquid centrifuge, a counter-current contact apparatus, aliquid-liquid extractor, a liquid-liquid continuous extractor, anextraction column, a static mixer, a coalescer, a homogenizer, or amixing/settling vessel.
 2. The method of claim 1 wherein the aromaticpolyether comprises the reaction product of at least one alkali metalsalt of a dihydroxy-substituted aromatic hydrocarbon with at least onesubstituted aromatic compound of the formula (I): Z(A¹—X¹)₂  (I)whereinZ is an activating radical, A¹ is an aromatic radical and X¹ is fluoro,chloro, bromo, or nitro.
 3. The method of claim 2 wherein the moiety—A¹—Z—A¹— is a bis(arylene)sulfone, bis(arylene)ketone,tris(arylene)bis(sulfone), tris(arylene)bis(ketone),bis(arylene)benzo-1,2-diazine, bis(arylene)azoxy radical, or a bisimideradical illustrated by the formula (VII):

wherein R⁸ is a substituted or unsubstituted C₆₋₂₀ divalent aromatichydrocarbon radical, a C₂₋₂₂ alkylene or cycloalkylene radical, a C₂₋₈bis(alkylene-terminated) polydiorganosiloxane radical or a divalentradical of the formula (VIII):

in which Q is isopropylidene, methylene,

or a covalent bond, or wherein Z is polyvalent and with A¹ forms part ofa fused ring system, a benzimidazole, benzoxazole, quinoxaline orbenzofuran.
 4. The method of claim 2 wherein the aromatic polyether isselected from the group consisting of polyethersulfones,polyetherketones, polyetheretherketones, and polyetherimides.
 5. Themethod of claim 4 wherein the aromatic polyether is an aromaticpolyetherimide.
 6. The method of claim 5 wherein the aromaticpolyetherimide comprises the reaction product of a bisphenol A moietywith at least one of 1,3-bis[N-(4-chlorophthalimido)]benzene,1,4-bis[N-(4-chlorophthalimido)]benzene,1,3-bis[N-(3-chlorophthalimido)]benzene,1,4-bis[N-(3-chlorophthalimido)]benzene,1-[N-(4-chlorophthalimido)]-3-[N-(3-chlorophthalimido)benzene, or1-[N-(4-chlorophthalimido)]-4-[N-(3-chlorophthalimido)benzene.
 7. Themethod of claim 1 wherein the catalyst is at least one member selectedfrom the group consisting of hexaalkylguanidinium salts andalpha,omega-bis(pentaalkylguanidinium)alkane salts.
 8. The method ofclaim 1 wherein the acid is selected from the group consisting oforganic acids, acetic acid, inorganic acids, phosphorous acid,phosphoric acid, and hydrochloric acid.
 9. The method of claim 1 whereinthe alkali metal halide is sodium chloride.
 10. The method of claim 1wherein the organic phase after any contact with and separation fromwater is heated to a temperature in a range of between about 110° C. andabout 150° C. and then cooled to less than 110° C. before any subsequentcontact with and separation from water
 11. The method of claim 1 whereinat least one water extraction comprises a static mixer/coalescercombination.
 12. The method of claim 1 wherein at least one waterextraction step comprises steam sparging.
 13. The method of claim 1wherein the organic solvent is o-dichlorobenzene.
 14. The method ofclaim 13 wherein a first water extraction is performed using phase ratioof o-dichlorobenzene to water of about 0.5-6:1 weight/weight.
 15. Themethod of claim 14 wherein the phase ratio of o-dichlorobenzene to wateris about 5:1 weight/weight.
 16. The method of claim 14 wherein a firstwater extraction is performed at a temperature of about 60-180° C. 17.The method of claim 16 wherein a first water extraction is performed ata temperature of about 85-105° C.
 18. The method of claim 13 wherein awater extraction following a first water extraction is performed usingphase ratio of o-dichlorobenzene to water of about 0.5-6:1weight/weight.
 19. The method of claim 18 wherein a water extractionfollowing a first extraction is performed at a temperature of about60-180° C.
 20. The method of claim 19 wherein a water extractionfollowing a first extraction is performed at a temperature of about85-105° C.
 21. The method of claim 13 wherein the water phase from anextraction is treated to recover catalyst.
 22. The method of claim 21wherein the catalyst is at least one member selected from the groupconsisting of hexaalkylguanidinium salts andalpha,omega-bis(pentaalkylguanidinium)alkane salts.
 23. The method ofclaim 1 further comprising at least one solid separation step followinga water extraction step.
 24. The method of claim 23 wherein a solidseparation step comprises at least one of a filtration step, acentrifugation step, or a decantation step.
 25. The method of claim 13further comprising at least one solid separation step following a waterextraction step.
 26. The method of claim 25 wherein a solid separationstep comprises at least one of a filtration step, a centrifugation step,or a decantation step
 27. The method of claim 26 wherein theo-dichlorobenzene phase is mixed and heated to a temperature between theboiling point of water and the boiling point of o-dichlorobenzene underthe prevailing pressure before at least one solid separation step. 28.The method of claim 27 wherein a portion of alkali metal halide is in aform that can be separated in a solid separation step following theapplication of heat.
 29. The method of claim 27 wherein theo-dichlorobenzene-comprising phase is heated to a temperature in a rangebetween about 110° C. and about 180° C. at atmospheric pressure.
 30. Amethod for purifying a mixture comprising (i) an aromatic polyetherreaction product made by a halide displacement polymerization process,(ii) a catalyst, (iii) an alkali metal halide, and (iv) a substantiallywater-immiscible organic solvent with boiling point at atmosphericpressure of greater than 110° C. and a density ratio to water of greaterthan 1.1:1 at 20-25° C., comprising the steps of: (a) subjecting themixture to at least one solid separation step; (b) quenching the mixturewith acid; and (c) extracting the organic solution at least once withwater.
 31. The method of claim 30 wherein the aromatic polyethercomprises the reaction product of at least one alkali metal salt of adihydroxy-substituted aromatic hydrocarbon with at least one substitutedaromatic compound of the formula (I): Z(A¹—X¹)₂  (I)wherein Z is anactivating radical, A¹ is an aromatic radical and X¹ is fluoro, chloro,bromo, or nitro.
 32. The method of claim 31 wherein the moiety —A¹—Z—A¹—is a bis(arylene)sulfone, bis(arylene)ketone, tris(arylene)bis(sulfone),tris(arylene)bis(ketone), bis(arylene)benzo-1,2-diazine,bis(arylene)azoxy radical, or a bisimide radical illustrated by theformula (VII):

wherein R⁸ is a substituted or unsubstituted C₆₋₂₀ divalent aromatichydrocarbon radical, a C₂₋₂₂ alkylene or cycloalkylene radical, a C₂₋₈bis(alkylene-terminated) polydiorganosiloxane radical or a divalentradical of the formula (VIII):

in which Q is isopropylidene, methylene,

or a covalent bond, or wherein Z is polyvalent and with A¹ forms part ofa fused ring system, a benzimidazole, benzoxazole, quinoxaline orbenzofuran.
 33. The method of claim 30 wherein the aromatic polyether isselected from the group consisting of polyethersulfones,polyetherketones, polyetheretherketones, and polyetherimides.
 34. Themethod of claim 33 wherein the aromatic polyether is an aromaticpolyetherimide.
 35. The method of claim 34 wherein the aromaticpolyetherimide comprises the reaction product of a bisphenol A moietywith at least one of 1,3-bis[N-(4-chlorophthalimido)]benzene,1,4-bis[N-(4-chlorophthalimido)]benzene,1,3-bis[N-(3-chlorophthalimido)]benzene,1,4-bis[N-(3-chlorophthalimido)]benzene,1-[N-(4-chlorophthalimido)]-3-[N-(3-chlorophthalimido)benzene, or1-[N-(4-chlorophthalimido)]-4-[N-(3-chlorophthalimido)benzene.
 36. Themethod of claim 30 wherein the catalyst is at least one member selectedfrom the group consisting of hexaalkylguanidinium salts andalpha,omega-bis(pentaalkylguanidinium)alkane salts.
 37. The method ofclaim 30 wherein the alkali metal halide is sodium chloride.
 38. Themethod of claim 30 wherein a solid separation step comprises at leastone of a filtration step, a centrifugation step, or a decantation step.39. The method of claim 38 wherein a solid separation step comprises afiltration step performed at a temperature in a range of between about25° C. and about 220° C.
 40. The method of claim 39 wherein a filtrationstep is performed at a temperature in a range of between about 60° C.and about 180° C.
 41. The method of claim 38 wherein a solid separationstep is performed using at least one of a dead-end filter, cross-flowfilter, liquid-solid cyclone separator, vacuum drum filter, bagcentrifuge, or vacuum conveyor belt separator.
 42. The method of claim30 wherein the acid is selected from the group consisting of organicacids, acetic acid, inorganic acids, phosphorous acid, phosphoric acid,and hydrochloric acid.
 43. The method of claim 30 wherein the organicsolvent is o-dichlorobenzene.
 44. The method of claim 43 wherein theo-dichlorobenzene phase is mixed and heated to a temperature between theboiling point of water and the boiling point of o-dichlorobenzene underthe prevailing pressure before at least one solid separation step. 45.The method of claim 44 wherein the o-dichlorobenzene phase is heated toa temperature in a range between about 110° C. and about 180° C. atatmospheric pressure.
 46. The method of claim 44 wherein a portion ofalkali metal halide is in a form that can be separated in a solidseparation step following application of heat.
 47. The method of claim43 wherein the o-dichlorobenzene phase is treated at least once with asolid medium to adsorb catalyst species before a solid separation step.48. The method of claim 47 wherein the o-dichlorobenzene phase istreated at least once with a solid medium to adsorb catalyst speciesafter substantial removal of alkali metal halide from the phase.
 49. Themethod of claim 47 wherein at least one catalyst is recovered from thesolid medium after solid separation.
 50. The method of claim 49 whereinthe catalyst is at least one member selected from the group consistingof hexaalkylguanidinium salts andalpha,omega-bis(pentaalkylguanidinium)alkane salts.
 51. The method ofclaim 47 in which the solid medium comprises silica.
 52. The method ofclaim 30 wherein the water phase from an extraction is treated torecover catalyst.
 53. The method of claim 52 wherein the catalyst is atleast one member selected from the group consisting ofhexaalkylguanidinium salts andalpha,omega-bis(pentaalkylguanidinium)alkane salts.
 54. A method forpurifying a mixture comprising (i) an aromatic polyether reactionproduct made by a halide displacement polymerization process, (ii) acatalyst, (iii) an alkali metal halide, and (iv) a substantiallywater-immiscible organic solvent with boiling point at atmosphericpressure of greater than 110° C. and a density ratio to water of greaterthan 1.1:1 at 20-25° C., comprising: at least one solid separation step,and at least one ion exchange step.
 55. The method of claim 54 whereinthe aromatic polyether comprises the reaction product of at least onealkali metal salt of a dihydroxy-substituted aromatic hydrocarbon atleast one substituted aromatic compound of the formula (I):Z(A¹—X¹)₂  (I)wherein Z is an activating radical, A¹ is an aromaticradical and X¹ is fluoro, chloro, bromo, or nitro.
 56. The method ofclaim 55 wherein the moiety —A¹—Z—A¹— is a bis(arylene)sulfone,bis(arylene)ketone, tris(arylene)bis(sulfone), tris(arylene)bis(ketone),bis(arylene)benzo-1,2-diazine, bis(arylene)azoxy radical, or a bisimideradical illustrated by the formula (VII):

wherein R⁸ is a substituted or unsubstituted C₆₋₂₀ divalent aromatichydrocarbon radical, a C₂₋₂₂ alkylene or cycloalkylene radical, a C₂₋₈bis(alkylene-terminated)polydiorganosiloxane radical or a divalentradical of the formula (VIII):

in which Q is isopropylidene, methylene,

or a covalent bond, or wherein Z is polyvalent and with A¹ forms part ofa fused ring system, a benzimidazole, benzoxazole, quinoxaline orbenzofuran.
 57. The method of claim 54 wherein the aromatic polyether isselected from the group consisting of polyethersulfones,polyetherketones, polyetheretherketones and polyetherimides.
 58. Themethod of claim 57 wherein the aromatic polyether is an aromaticpolyetherimide.
 59. The method of claim 58 wherein the aromaticpolyetherimide comprises the reaction product of a bisphenol A moietywith at least one of 1,3-bis[N-(4-chlorophthalimido)]benzene,1,4-bis[N-(4-chlorophthalimido)]benzene,1,3-bis[N-(3-chlorophthalimido)]benzene,1,4-bis[N-(3-chlorophthalimido)]benzene,1-[N-(4-chlorophthalimido)]-3-[N-(3-chlorophthalimido)benzene, or1-[N-(4-chlorophthalimido)]-4-[N-(3-chlorophthalimido)benzene.
 60. Themethod of claim 54 wherein the alkali metal halide is sodium chloride.61. The method of claim 54 wherein a solid separation step comprises atleast one of a filtration step, a centrifugation step, or a decantationstep.
 62. The method of claim 61 wherein a solid separation stepcomprises a filtration step performed at a temperature in a range ofabout between about 25° C. and about 220° C.
 63. The method of claim 62wherein a filtration step is performed at a temperature in a range ofbetween about 60° C. and about 180° C.
 64. The method of claim 54wherein the ion exchange step employs an ion exchange resin.
 65. Themethod of claim 64 wherein the ion exchange resin is treated to recovercatalyst.
 66. The method of claim 65 wherein the catalyst is at leastone member selected from the group consisting of hexaalkylguanidiniumsalts and alpha,omega-bis(pentaalkylguanidinium)alkane salts.
 67. Themethod of claim 54 wherein the organic solvent is o-dichlorobenzene. 68.The method of claim 54 further comprising at least one water extractionstep.
 69. The method of claim 68 wherein the mixture is quenched withacid before at least one water extraction step.
 70. The method of claim69 wherein the acid is selected from the group consisting of organicacids, acetic acid, inorganic acids, phosphorous acid, phosphoric acid,and hydrochloric acid.
 71. A method for purifying a mixture comprising(i) an aromatic polyether reaction product made by a halide displacementpolymerization process, (ii) a catalyst, (iii) an alkali metal halide,and (iv) a substantially water-immiscible organic solvent with boilingpoint at atmospheric pressure of greater than 110° C. and a densityratio to water of greater than 1.1:1 at 20-25° C., comprising the stepsof: (a) providing to the mixture an amount of water in a range betweenabout 0.005 wt. % and about 10 wt. % based on weight of polyether; (b)mixing the phases, wherein a portion of alkali metal halide is in a formthat can be separated by a solid separation step following mixing; and(c) subjecting the mixture to at least one solid separation step. 72.The method of claim 71 wherein the aromatic polyether comprises thereaction product of at least one alkali metal salt of adihydroxy-substituted aromatic hydrocarbon with at least one substitutedaromatic compound of the formula (I): Z(A¹—X¹)₂  (I)wherein Z is anactivating radical, A¹ is an aromatic radical and X¹ is fluoro, chloro,bromo, or nitro.
 73. The method of claim 72 wherein the moiety —A¹—Z—A¹—is a bis(arylene)sulfone, bis(arylene)ketone, tris(arylene)bis(sulfone),tris(arylene)bis(ketone), bis(arylene)benzo-1,2-diazine,bis(arylene)azoxy radical, or a bisimide radical illustrated by theformula (VII):

wherein R⁸ is a substituted or unsubstituted C₆₋₂₀ divalent aromatichydrocarbon radical, a C₂₋₂₂ alkylene or cycloalkylene radical, a C₂₋₈bis(alkylene-terminated)polydiorganosiloxane radical or a divalentradical of the formula (VIII):

in which Q is isopropylidene, methylene,

or a covalent bond, or wherein Z is polyvalent and with A¹ forms part ofa fused ring system, a benzimidazole, benzoxazole, quinoxaline orbenzofuran.
 74. The method of claim 71 wherein the aromatic polyether isselected from the group consisting of polyethersulfones,polyetherketones, polyetheretherketones, and polyetherimides.
 75. Themethod of claim 74 wherein the aromatic polyether is an aromaticpolyetherimide.
 76. The method of claim 75 wherein the aromaticpolyetherimide comprises the reaction product of a bisphenol A moietywith at least one of 1,3-bis[N-(4-chlorophthalimido)]benzene,1,4-bis[N-(4-chlorophthalimido)]benzene,1,3-bis[N-(3-chlorophthalimido)]benzene,1,4-bis[N-(3-chlorophthalimido)]benzene,1-[N-(4-chlorophthalimido)]-3-[N-(3-chlorophthalimido)benzene, or1-[N-(4-chlorophthalimido)]-4-[N-(3-chlorophthalimido)benzene.
 77. Themethod of claim 71 wherein the catalyst is at least one member selectedfrom the group consisting of hexaalkylguanidinium salts andalpha,omega-bis(pentaalkylguanidinium)alkane salts.
 78. The method ofclaim 71 wherein the mixture is quenched with acid.
 79. The method ofclaim 78 wherein the acid is selected from the group consisting oforganic acids, acetic acid, inorganic acids, phosphorous acid,phosphoric acid, and hydrochloric acid.
 80. The method of claim 71wherein the organic phase after any contact with and separation fromwater is heated to a temperature in a range of between about 110° C. andabout 150° C. and then cooled to less than 110° C. before any subsequentcontact with and separation from water
 81. The method of claim 71wherein the organic solvent is o-dichlorobenzene.
 82. The method ofclaim 71 wherein the alkali metal halide is sodium chloride.
 83. Themethod of claim 71 wherein the solid separation step comprises at leastone of a filtration step, a centrifugation step, or a decantation step.84. The method of claim 71 wherein the phases are mixed and heated to atemperature between the boiling point of water and the boiling point oforganic phase under the prevailing pressure before at least one solidseparation step.
 85. The method of claim 84 wherein a portion of alkalimetal halide is in a form that can be separated in a solid separationstep following the application of heat.
 86. The method of claim 83wherein a solid separation step comprises a filtration step performed ata temperature in a range of about between about 25° C. and about 220° C.87. The method of claim 86 wherein a filtration step is performed at atemperature in a range of between about 60° C. and about 180° C.
 88. Themethod of claim 71 further comprising the step of treating the organicphase at least once with a solid medium to adsorb catalyst species. 89.The method of claim 88 wherein at least one catalyst is recovered fromthe solid medium after solid separation.
 90. The method of claim 89wherein the catalyst is at least one member selected from the groupconsisting of hexaalkylguanidinium salts andalpha,omega-bis(pentaalkylguanidinium)alkane salts.
 91. The method ofclaim 88 in which the solid medium comprises silica.
 92. A method forpurifying a mixture comprising (i) an aromatic polyetherimide comprisingthe reaction product of bisphenol A disodium salt and at least one of1,3-bis[N-(4-chlorophthalimido)]benzene or1,3-bis[N-(3-chlorophthalimido)]benzene, (ii) hexaethylguanidiniumchloride catalyst, (iii) sodium chloride, and (iv) o-dichlorobenzene,comprising the steps of: (a) quenching the mixture with acid; and (b)extracting the organic solution at least once with water.
 93. The methodof claim 92 wherein the acid is selected from the group consisting oforganic acids, acetic acid, inorganic acids, phosphorous acid,phosphoric acid, and hydrochloric acid.
 94. The method of claim 92wherein the water phase from an extraction is treated to recoverhexaethylguanidinium chloride catalyst.
 95. The polyetherimide productpurified by the method of claim 92 containing less than 100 ppm sodium.96. A method for purifying a mixture comprising (i) an aromaticpolyetherimide comprising the reaction product of bisphenol A disodiumsalt and at least one of 1,3-bis[N-(4-chlorophthalimido)]benzene or1,3-bis[N-(3-chlorophthalimido)]benzene (ii) a hexaethylguanidiniumchloride catalyst, (iii) sodium chloride, and (iv) o-dichlorobenzene,comprising the steps of: (a) subjecting the mixture to at least onesolid separation step; (b) quenching the mixture with acid; and (c)extracting the organic solution at least once with water.
 97. The methodof claim 64 wherein a solid separation step comprises a filtration stepperformed at a temperature in a range of about between about 25° C. andabout 220° C.
 98. The method of claim 96 wherein the acid is selectedfrom the group consisting of organic acids, acetic acid, inorganicacids, phosphorous acid, phosphoric acid, and hydrochloric acid.
 99. Themethod of claim 96 wherein the water phase from an extraction is treatedto recover hexaethylguanidinium chloride catalyst.
 100. Thepolyetherimide product purified by the method of claim 96 containingless than 100 ppm sodium.
 101. A method for purifying a mixturecomprising (i) an aromatic polyetherimide comprising the reactionproduct of bisphenol A disodium salt and at least one of1,3-bis[N-(4-chlorophthalimido)]benzene or1,3-bis[N-(3-chlorophthalimido)]benzene, (ii) a hexaethylguanidiniumchloride catalyst, (iii) sodium chloride, and (iv) o-dichlorobenzene,comprising:at least one solid separation step, and at least one ionexchange step, comprising an ion exchange resin.
 102. The method ofclaim 101 wherein a solid separation step comprises a filtration stepperformed at a temperature in a range of about between about 25° C. andabout 220° C.
 103. The method of claim 101 wherein the ion exchangeresin is treated to recover catalyst.
 104. The polyetherimide productpurified by the method of claim 101 containing less than 100 ppm sodium.105. A method for purifying a mixture comprising (i) an aromaticpolyetherimide comprising the reaction product of bisphenol A disodiumsalt and at least one of 1,3-bis[N-(4-chlorophthalimido)]benzene or1,3-bis[N-(3-chlorophthalimido)]benzene, (ii) hexaethylguanidiniumchloride catalyst, (iii) sodium chloride, and (iv) o-dichlorobenzene,comprising the steps of: (a) providing to the mixture an amount of waterin a range between about 0.005 wt. % and about 10 wt. % based on weightof polyether; (b) mixing the phases, wherein a portion of alkali metalhalide is in a form that can be separated by a solid separation stepfollowing mixing; and (c) subjecting the mixture to at least one solidseparation step.
 106. The method of claim 105 wherein the mixture isquenched with acid.
 107. The method of claim 106 wherein the acid isselected from the group consisting of organic acids, acetic acid,inorganic acids, phosphorous acid, phosphoric acid, and hydrochloricacid.
 108. The method of claim 105 wherein a solid separation stepcomprises a filtration step performed at a temperature in a range ofabout between about 25° C. and about 220° C.
 109. The method of claim105 further comprising the step of treating the organic phase at leastonce with silica gel to adsorb catalyst species.